Hydrometry and slide rules in brewing and...

15Brewery History Number 124/5

Hydrometry and slide rules in brewing and distilling

Tom Martin

‘Many other pretty things he showed us,and did give me a glass bubble to try thestrength of liquors with.’

Samuel Pepys and his wife seeingBoyle's densimeter at Mr Spong's,December, 1668.

Introduction

The term hydrometer was often usedinterchangeably with aerometer by earlydevelopers of this instrument but aerom-etry is now associated with determiningthe density of gases and hydrometry, inaddition to the determination of the den-sity of liquids, has become associatedwith determination of water flow or evenused as an alternative to hygrometry i.e.measurement of humidity.

The exact history of the hydrometer isunclear. There is conjecture that aninstrument of this type was used byArchimedes and Hypatia of Alexandria isascribed as inventor of the aerometer inAD 415. Whatever the truth, these earlyinstruments appear to have lapsed intoobscurity and the renaissance of thehydrometer is attributed to Robert Boylewho, in 1675, described his New EssayInstrument, a bubble furnished with a

long and slender stem, to the RoyalSociety.1

The story of the simple hydrometer hasinteresting similarities to that of the sliderule. Developed by Boyle in 1675, about50 years later than Oughtred's inventionof the slide rule, it continued in wide-spread use until the 1970s when, as theslide rule gave way to the pocket calcula-tor, much use of the hydrometer wasreplaced by electronic density metersand by rapid advances in instrumentalmethods of analysis. Like the slide rule,early impetus to development came fromCustoms and Excise who were anxiousto find accurate ways of measuring alco-holic strength and protecting the rev-enue. Again, as with the slide rule, use ofdedicated hydrometers spread into manytraditional industries and in the earlyyears hydrometer and slide rule manu-facture was carried out side by side bythe scientific instrument makers.

The hydrometer can do no more thanmeasure the specific gravity or density ofa liquid and there have been many rec-ommendations that translation of suchmeasurements to estimates of solutionconcentration or other properties relatedto density should be carried out separate-ly, by calculation, or reference to tables.

16 Journal of the Brewery History Society

Nevertheless a number of different densi-ty scales became established over theyears and hydrometers indicating theconcentration of specific compoundswere developed for commerce andprocess control. Table 1 illustrates therange of instruments offered in old salescatalogues.

Given the historical, wide-spread use ofhydrometers one might expect to find astrong association between these instru-ments and industry related slide rules. Infact it is difficult to find any examples out-

side Customs & Excise and the brewingand distilling industries. The wide rangeof slide rules used in the alcohol industryhas been surveyed by Hopp2 at the 1999International Meeting in Cambridge anddiscussion here will be limited to thosedirectly associated with hydrometermeasurements.

Many works on the history of the fermen-tation industry give some account of thedevelopment of the hydrometer and itseffect on both revenue legislation andproduct standardisation. Specific texts

Name Use

Alcoholometer DistillingSaccharometer BrewingSamson CiderBrix Sugar refining, Confectionery Acetometer VinegarAcidimeter Acids, BatteriesCitrometer Lime juice etc.Salinometer Steam raising boilersSalometer Brine picklingBrinometer Ice makingLactometer MilkAmmoniameter RefrigerationBarktometer TanningOleometer Linseed, rape, sperm oils etc.Oil hydrometer Oil and petrolMarine Hydrometer Sea water (Load Line Act)Urinometer MedicalSoil Meter Particle sizeTwaddell scale General industryBaume light scale dittoBaume heavy scale ditto

Table 1: Examples of Industrial Hydrometers


include Scarisbrick,3 an excise officer, onspirit assaying (1898) and Tate,4 of theLaboratory of the Government Chemist,on alcoholometry (1930). A recent publi-cation5 is a history of the Customs andExcise, 1640-1845, by Ashworth (2003).Ashworth notes how the science ofmetrology (e.g. hydrometry) went handin hand with increasing legal definition ofthe commodity and how the develop-ment of instruments for commercial pur-poses needed to be considered in rela-tion to political debates, government poli-cies, the actions of interest groups andsocial relations. The details of theseissues are outside the scope of this shortpaper but they had a major influence onthe selection of instrumentation by theExcise. The picture is further complicat-ed by the former independence of theregional excise authorities within theUnited Kingdom. The Treaty of Unionbetween England and Scotland in 1707provided that the same duties in excis-able liquors should be levied in Scotlandas applied in England. However, theEnglish and Scottish Boards of Excisecontinued to exist and spirit duties werenot harmonised until 1855. Ireland alsoacted independently until the Act ofUnion in 1801. This independence fos-tered competing instrument develop-ments and definitions of alcoholicstrength with much vested skull-duggery.Differences in the basis of duty paymentalso resulted in separate developmentsof the distiller's spirit hydrometer and thebrewer's saccharometer, the formerbeing fiscal duty led and the latter a laterand initially, commercial and processcontrol innovation.

The spirit hydrometer

The principal problems relating to themeasurement of the strength of alcoholsolutions have been:

· Mixtures of alcohol and water are notadditive but a net contraction of volumeoccurs on mixing. Within the trade this isreferred to as the ‘bulk contraction.’· With increasing temperature, alcoholexpands much more rapidly than waterthus altering the volumetric ratio of thetwo components.· In hydrometry, expansion of the hydrom-eter bulb with temperature and pressureand also solution viscosity affect theinstrument reading.· It was relatively late in the 19th centurybefore the specific gravity of pure anhy-drous alcohol was established. The term'proof' thus developed as a series of qual-itative and then arbitrarily quantified stan-dards, associated with developments inchemistry and instrumentation.

After Boyle, hydrometers began to beproduced by a variety of makers, first asacademic instruments, later attracting theattention of both Customs and Excise toassist in checking the strength of spirits.They were calibrated generally so thatthe middle of the stem became sub-merged in ‘proof,’ an equal mixture ofwater and the strongest spirit thenknown. The first models were made ofglass or, naively, turned from box wood orivory.

John Clarke, a ‘Turner and EngineMaker’ of Charing Cross, is recorded as


the person who took matters a stage fur-ther by devising a system to quantify con-centrations above and below proof andalso providing a system of notation. Thiswas described in a paper to the RoyalSociety in 17306 (Fig. 1). After several tri-als with ivory he realised that this materi-al absorbed alcohol and he made a metalhydrometer with a quarter-inch diameterbrass wire going through and soldered toa copper ball. As shown in the figure, thehydrometer sank to mark 'M' in proof spir-it. The marks 'A' and 'B' indicated whetherthe spirit was either one-tenth over orunder proof meaning that one gallon ofwater 'added' to or 'removed' from tengallons of the spirit would bring it to proof.By screwing on a wide range of weightsat 'C' the entire range of spirit strengthcould be covered.

The Government was now showingincreasing interest in a good hydrometerfor fiscal purposes and instrument mak-ers began to take notice, hoping to pro-duce a hydrometer approved by the rev-enue. In 1759 Martin produced a hydrom-eter with 9 weights that claimed to indi-cate specific gravity. This was supportedby a small book to bring his work to theattention of the public. To convert hishydrometer readings to spirit strengthMartin supplied a slide rule or ‘Scale ofLines’ with each instrument. He alsoadvanced on Clarke by correcting fortemperature, using a special series ofnumbers on his Scale of Lines. Clarkecame back by adding a series of five 'air'or 'weather' weights. These were used forcorrecting for air temperature and were

termed 'very cold' (32-41ºF), 'cold' (41-50ºF), 'temperature' (50ºF), 'warm' (50-65ºF), 'very warm' (65-80ºF). AlthoughClarke's instrument appears to havebeen in use for a number of years, thefirst official mention of a hydrometer bythe Excise was in 1761 when Clarke'swas adopted as standard. Clarke'sweather weights were now increased to

Figure 1. Clarke’s hydrometer, 1730,(Scarisbrick(3))


eleven and to make his hydrometer moreuseful Clarke added a series of 'per cent'weights for import staff and another setfor testing weak spirits in distilleries.Clarke's hydrometer now used:

23 gravity weights11 weather weights9 per cent weights11 weak spirits weights

54 in all. Other modifications included afixed lower bulb on which the weightswere suspended rather than screwed. Anexample held in the Customs & ExciseNational Museum is shown in Fig. 2.

Clarke's hydrometer continued to because for complaint, the defects incur-

able and his adopted notation cumber-some. In spite of these shortcomings, useof Clarke's hydrometer was recognisedby statute in 1787 and made permanentin 1801. Tate4 shows an example ofabout 1815 with 140 weights and it isreported that a final version even used300 weights.

In passing it is interesting to note that onClarke's death his business passed to hisson Richard who married the sister ofJohn Dring. Dring later took over thebusiness in partnership with WilliamFage. They adopted Clarke's 'half moonand dagger mark' and formed the compa-ny Dring & Fage, so well known for itsslide rules and other instruments for thenext 150 years.

Figure 2. Clarke's hydrometer with 42 weights. Reproduced with permission of the NationalMuseums Liverpool (Customs & Excise National Museum)


At the same time as recognising Clarke,the 1787 Act declared it expedient thatexperiments should be made to find asuitable instrument for estimating spiritvalues for revenue purposes, a taskassigned to the Royal Society. Over thenext 15 years a series of reports wereproduced on the accurate determinationof the specific gravity of alcohol andwater mixtures but the Society's quest fora new instrument was not advanced.Acrimony over duty charges based onClarke increased and at this time theExcise authorities in England, Scotlandand Ireland were following separateroutes. The hydrometer of William Speer,surveyor and assayer of spirits in the Portof Dublin was adopted in Ireland in 1802and the USA had adopted the hydrome-ter of Dicas of Liverpool as the standardin 1790. The Act of Union of 1801 gaveimpetus to seeking a common base forduty payment for Britain and Ireland andin 1802 an act was passed ‘To authorisethe Lord High Treasurer orCommissioners of the Treasury in GreatBritain and the Lord High Treasurer orCommissioners of the Treasury in Irelandto Order the Use of the Hydrometers nowemployed in the Management of theRevenue to be discontinued and otherinstruments to be used instead thereof’

A Committee of Enquiry was appointedand this placed advertisements in thepublic press. It is reported that 19 instru-ments were submitted with some makersproviding more than one type. TheCommittee then instructed ‘That everyperson who has sent in more than one

hydrometer be desired to withdraw everyinstrument but that on which he is meantto rely’. The principal competitors seemto have been -· Dicas - the USA standard, submitted byMiss M Dicas, daughter of George Dicaswho had died. It had 36weights· William Speer - hydrometer adopted inIreland· James & George Quin - this hadreceived official acceptance for use andhad 7weights· Atkins & Co - instrument makers· Clarke's Centigrade - This was a muchsimplified version developed by Dring &Fage using only 4 weights. Centigradedid not refer to temperature but that theinstrument covered the full range of alco-hol concentration in 100 units.· Dring - own design· Miller & Adie - instrument makers whosubmitted an instrument combining theprinciples of the hydrometer and thehydrostatic balance.· Mrs Andoe · Saunders· Bartholomew Sikes - a hydrometer ofgilded brass with 9 weights

The final assessment was reduced tonine instruments and it has been sug-gested that these had marked similari-ties, varying mainly in their methods oftemperature compensation. Quin'sattempts to establish the ground rules arerecorded in a later memoir by him (report-ed in Scarisbrick3):

‘Construction of the Hydrometer andSliding Rule:- In the first place it was nec-


essary to know at what the Governmenthad determined to fix hydrometer proof.For this purpose I waited on Mr Vanisttart(now Chancellor of the Exchequer) at theTreasury who then honoured me with aninterview and informed me that the Lordsof the Treasury had agreed to fix hydrom-eter proof at 0.920 specific gravity, 60º ofheat, considering pure water to be 1.000specific gravity, at the same temperature,consequently all the different strengthsshould agree with these two points.’

This was scientifically sound for the timebut as we shall see this is nothing like thefinal outcome. A description of Quin's 7-weight hydrometer is given in Boyle's ThePublican and Spirit Dealer's Companion,1800,7 as shown in Fig. 3.

A description of Clarke's Centigrade,Dring & Co., 4-weight hydrometer andslide rule is given also by Boyle as shownin Fig. 4.

The point of most interest to this paper isthat all competitors, with the exception ofSikes, had provided hydrometers withaccompanying slide rules. Sikes, instead,presented the examiners with a hydrom-eter and a table of six pages. Sikes wasa man of 73 who had entered the Excisein 1754 and had followed the develop-ment of the hydrometer closely. As some-time Secretary to the Board of Excise hewas well aware of the controversy sur-rounding Clarke's instrument and is cred-ited with solving most of its faults beforeit was abandoned. In developing his sys-tem, Sikes used his detailed knowledgeof studies on the density of alcohol/water

mixtures. With a hydrometer (Fig. 5)scaled in 10 units, graduated at 0.2 unitintervals and 9 additional weights he cov-ered the then known range of alcoholconcentration in 500 steps. His hydrome-ter scales have no defined unit of meas-urement but provide a reading, termed an‘indication.’ The tables converted thisindication, at the temperature of meas-urement, to percentage proof alcohol at50º Fahrenheit and so allowed a true rev-enue charge to be levied.

In an evaluation of the various instru-ments submitted, over a limited range ofconcentration and temperature, Sikes'hydrometer was neither the fastest normost accurate. It was, however, consid-ered the easiest to handle in inexperi-enced hands, suitable for travellingexcise men and the tables gave directlythe units on which duty was payable. AsScarisbrick noted of Sikes' competitors:

‘They bent their energies towards makinga perfect instrument, while neglecting theequally urgent and important matter, viz.,that of furnishing a perfect method oftranslating its indications into expressionof strength.’

Sikes hydrometer and new system forexpressing ‘proof’ gave a value for proofalcohol close to that of Clarke and theExcise Commissioners asked him tomodify his system to minimise anychange in the duty base. After furthertests and calculations a compromise wasagreed to accord with the tables andproof spirit became defined as ‘that atwhich at the Temperature of 51 Degrees


Figure 3. Directions for use of Quin's 7-weight hydrometer as described by Boyle.7


Figure 4. Directions for use of Clarke's centigrade hydrometer and slide rule as described byBoyle.7


by Fahrenheit's Thermometer weighsexactly twelve thirteenths of an equalmeasure of Distilled Water.’ When welook at Sikes hydrometer we see the ninecircular weights which slot onto the lowerstem. In addition we have a square capwhich fits on top of the stem. With the ‘60’weight applied, the hydrometer will read‘proof’ at 60.8 at 51ºF. If the cap, whichweighs one twelfth of the combinedweight of the hydrometer and ‘60’ weight,is added the hydrometer will now sink tothe same point in distilled water at the

same temperature to prove the accuracyof the instrument.

Although Sikes' hydrometer and tableswere recommended for fiscal use in 1803they did not finally replace Clarke's until1816. partly due to the need to make anadequate number of instruments. The Actof 1816 was provisional one authorisinguse of the hydrometer and tables until1818. This Act also authorised the use of‘three accurate scales or sliding rules’ foruse with the hydrometer - a very rare

Figure 5. Sikes' hydrometer with thermometer and proof and comparative slide rules


case of slide rules being enshrined in anAct? The first rule was to allow calcula-tion of the volume of spirit at onestrength to the equivalent volume at anyother strength. The second rule was forstock control in distilleries where dis-tillers were allowed 19 gallons at 8%over proof for every 100 gallons of wash.The third rule was for use at rectifierswhere a standard of 28% under proofwas in use.

The hydrometer and tables werelegalised, finally, in the Hydrometer Act of1818, when ‘From and after the passingof this Act, all spirits shall be deemed andtaken to be of the degree of strength atwhich the said hydrometer, called SikesHydrometer, used under the direction ofthe Commissioners of Excise, shall, upontrial by any Officer or Officers of theCustoms or Excise denote such spirits tobe ...’ For some reason use of the sliderules was not renewed in this Act.

A number of mysteries surround Sikes'work:· It is suggested that his design wastaken from a continental model or a mod-ified form of Clarke's Centigradehydrometer.· He did not make his own instrumentsbut appeared to use several othersincluding his competitor, Atkins.· He provided no details of the basis ofhis calculations to the Committee ofEnquiry or the Commissioners.In 1803 Sikes petitioned theCommissioners to be the supplier of hishydrometer but died suddenly that yearbefore a contract was made.

We now come to another significant fam-ily connection. Sikes' daughter AnnaMaria married the nephew of Sikes' wife,one Robert Brettell Bate who became thewell known instrument maker ‘Bate of thePoultry.’ A recent monograph by AnitaMcConnell8 surveys Bate's life and work,including his association with thehydrometer makers of the time. On Sikes'death his wife made a series of petitionsfor both a lump sum in recognition ofSikes' work and also, in competition withAtkins, Speer and Dicas, the right to sup-ply. She pointed out that she held allSikes notebooks and tables and that herson-in-law and nephew, Bate, could man-ufacture them. After much prevarication,in 1810, she received £2,000 and thesupply agreement which lasted until herdaughter's death in 1851. As McConnellsays, this was a licence to print moneyand underpinned Bate's business for therest of his life.

Sykes hydrometers and books of tablesvery rarely have dates and it is impossi-ble to tie a book to an instrument.Eventually they became made by a widerange of suppliers; Buss, who claimed tobe successor to Bate, Dring & Fage,Long, Blake, Lumley, etc. but it is likelythat hydrometers not bearing Bate'sname are post 1851. There was also alarge business in repairing and adjustinghydrometers and hydrometer boxesbecame over-stamped with the adjuster'sname.

Although Sikes produced only a set oftables it is evident that, in addition tothose authorised in the 1816 Act, slide


rules for use with the hydrometer soonbecame available. Throughout the historyof the instrument, manufacturers offeredhydrometer boxes (Fig. 5) containingnone, one or two rules, approximately 9inches long in boxwood or ivory. The tworules became known as ‘The Proof Rule’and ‘The Comparative Rule.’ Batedescribes versions of both of these in the3rd edition of Sikes' tables (undated)where he also describes himself as ‘Onlyrepresentative of the inventor, HYDROM-ETER MAKER for the USE of THE REV-ENUE OF THE UNITED KINGDOM.’

Bate's proof rule allowed calculation of %proof at 51ºF from the hydrometer indica-tion and temperature between 30º and80º. He also provided a pair of log lines -‘The finely divided lines on the fourthedge of the slide and side are logarithmicnumbers, usually called multiplying lines,but so arranged as to admit of a singleradius performing the office commonlyassigned to two, which affords double theusual length to each several division.’This log line does not seem to have beenadopted generally and later rules asshown in Fig. 6 only provide ‘proof’ fromhydrometer indication and temperature.The slide rule is unable to compensatefor the full range of the tables and use islimited to between 35% under proof to55% over proof. Weak and strong spiritsstill can only be measured by referenceto the tables.

The comparative rule has two functions.As expressed by Bate:Costing - ‘The Slide contains the Strength

Figure 6. Bate's proof rule (ivory)(actual size 225 x 35mm)


of the Spirits from 70 per cent Over Proofto 70 per cent Under Proof and the linesA, B, shew the Comparative VALUES ofthose strengths in Shillings and Pence.’Reducing - ‘The lines C, D, shew theComparative QUANTITIES of Spirits withreference to their Strengths upon theSlide.’

This rule changed little from its originaldesign. As shown in Fig. 7. On the cost-ing side the slide runs from 70% underproof to 70% over proof. The lower stockruns from one shilling and sixpence to 8shillings per gallon and the upper stockfrom 6 to 30 shillings. In later versions ofthe rule, as duty increased, the stocksrun from 6 to 30 and from 20 to 100shillings. On the reducing side, the slideagain runs from 70% under to 70% overproof. The lower stock runs from 20 to100 gallons and the upper from 60 to 300gallons. This side does not appear tohave changed throughout the life of theinstrument and surprisingly, contains acardinal error. It treats dilution or concen-tration of spirits as a direct mathematicalratio and makes no allowance for the bulkcontraction factor. This correctionappeared only on later specialist tradeslide rules such as those of Farmar in theearly 20th century.

Sikes hydrometer and definition of proofprovided the basis of duty payment forwines and spirits for the next 160 yearswith various modifications.

It was recognised that only Sikes' tablehad any legislative authority and in 1833Bate proposed a table of specific gravity

Figure 7. Bate's comparative rule (ivory)(actual size 225 x 35mm)


expressed as pounds per gallon at 62ºFwhich was legalised in 1855. This Table ispicked up on Farmar's Spirit Rule (but nothis other rules) as a line correlating proofspirit with pounds per gallon at 62ºF. TheFinance Act of 1901 allowed the Customsand the Excise to regulate other meansof determining alcoholic strength and in1907 official tables were published relat-ing spirit strength to specific gravity. Astechnology developed, higher concentra-tions of alcohol than those recognised bySikes became available and the range ofworking temperatures widened. A supple-mentary Sikes 'A' hydrometer waslegalised in 1915 and a further 'B'hydrometer which, with a poise, could actas an 'A' hydrometer was adopted in1930.

Sikes and proof finally succumbed to theEuropean Union in 1980, being replacedby the OIML system of measuring alcoholby volume and mass.

This section of the paper has given a verysimplified account of the development ofthe legally defined measurement of alco-hol in the UK. There were of course manyother issues such as ‘obscuration’ whichcould include addition of substancessuch as sugar to alter the specific gravityand defeat the revenue or be an entirelylegitimate factor as with sugar residues inrum. With improving definition of the rela-tion of proof to specific gravity, sets ofglass hydrometers reading Sikes' indica-tion became available. These requiredspecial versions of Sikes' table to allowfor the different expansion of glass and,

as such were adopted as the officialmethod by the Indian Government. Manymanufacturers produced glass hydrome-ters giving a direct reading of proof spiritbut no one argued with the excise manand his little brass instrument!

The brewer’s saccharometer

Brewer's interest in the hydrometerdeveloped much later than in the distillingindustry and from a different standpoint.

John Richardson9 is generally creditedwith the introduction of the hydrometer tobrewers in 1784 coining the term ‘sac-charometer’ through its use to measurethe ‘saccharin’ or fermentable extract inbrewers' worts.

There were, however, earlier develop-ments. The first recorded interest is thatof Reddington who proposed a simpleinstrument for estimating the commercialvalue of beer: ‘As many shillings as you value your Beerat, so many Divisions you should makebetween the Height to which theInstrument rises in the Water, and theheight to which it rises in the Beer. By thismethod you may estimate what propor-tion the value of any Beer bears to theprice of the Strongest ... ’10

In 1762 Benjamin Martin made a hydrom-eter calibrated in specific gravity which headvertised as ‘useful in discovering thestrength of beer, ale, wine and worts.’ Inhis experiments, however, he became so


confused with his mass of data that heconsidered the instrument of no use.The entrepreneurial brewer JamesBaverstock11 purchased one of Martin'shydrometers in 1768. Baverstock hadobtained, already, a thermometer in 1762which ‘he was forced to conceal and touse by stealth, his father objecting vehe-mently to such 'experimental innovations.’

Using a much more systematic approachBaverstock demonstrated the value of thehydrometer in determining the strength ofbrewers' worts, work which the disillu-sioned Martin was unwilling to accept asof any value. Baverstock then obtained anintroduction to Samuel Whitbread whoalso dismissed the matter saying "gohome, young man, attend to your busi-ness and do not engage in such visionarypursuits".

Baverstock subsequently met the muchmore enlightened brewer Henry Thraleand conducted experiments for him, oftenin the presence of Thrale's friend, DrSamuel Johnson. Thrale gave his opinionthat ‘the hydrometer is an instrument ofgreat use to the brewer in various parts ofhis business’ and Johnson added hisapprobation ‘tending to render that a sci-entific and practical pursuit which hadhitherto been considered a practical oper-ation, requiring neither superior skill norjudgement.’

In spite of the value of his workBavenstock failed to attract wider interestand only published his HydrostaticalObservations and Experiments in theBrewery12 in 1785, as a response to

Figure 8. Richardson's saccharometer (afterBooth13). Scale b-c, range -1lb/brl, divisions - 0.1lb/brl.Water ‘regulator’ g.Weights equivalent to 1,2,3,4,5,10,20, or 30lb/brl applied at d.


Richardson's claims to originality in 1784when he published his StatisticalEstimates.

Although Baverstock's tardy publicationdid bring him much interest it wasRichardson's instrument that attracted theinterest of the larger brewers possibly part-ly due to the name and also the unit ofmeasurement that he adopted and thesaccharometer is frequently referred to as‘the brewers' compass’ in the older brew-ing texts.

The driving force behind Richardson'swork was quantifying the quality and yieldof extractable matter from malt. As a unithe adopted the term ‘brewers' pounds’which he defined as the number of poundsby which a barrel of wort exceeded the360 lb of an equivalent barrel of water

(lb/brl). At this time Richardson assumedthat the weight of water and extract wereadditive, i.e. he did not allow for the partialdisplacement of water by extract. Thusalthough he obtained relative values forthe yield of extract from malts they werenot absolute. Nevertheless the termbecame widely adopted and generallyused in the industry for almost 200 years.

Richardson's saccharometer is illustratedin Figs. 8 & 9. The first instruments had astem scale of 1lb and the range wasincreased by adding weights at the top ofthe stem. Richardson also recognised thatbrewing water had a density greater thanthat of distilled water and he introduced a‘regulator’. The lower hollow stem couldbe lengthened or shortened by a slidingtube which altered the volume withoutchanging the mass to give a zero value for

Figure 9. Richardson's saccharometer by Buss. Later model calibrated in specific gravity.


any particular water. This feature wasnotoriously difficult to make watertight forlong term use and was eventually aban-doned.

Richardson's work led to the larger brew-ers making major changes in malting andbrewing practice and standardisation ofproduct strength. Richardson is said,also, to have suffered financially from tra-ditionalists suspicious of his activities andthe saccharometer was not adopted bysmaller country brewers for many years.

The ability to measure wort strengthresulted in discussions on the payment ofexcise duty on beer according to specific

gravity, but nothing came of it. A simpli-fied history of excise duty on beer isshown in (Table 2). The Excise continuedto charge duty on beer according to itsclassification of ‘strong,’ ‘small’ or ‘table.’Beer duty itself was withdrawn in 1830and it was not until 1880 that Gladstonere-introduced a duty on beer, this timebased on the specific gravity, termed‘original gravity,’ of the wort.

In the absence of any Excise imperativea range of competing saccharometersappeared on the market. Accum14 in1820 noted that the principal instrumentswere those of Dicas which was calibratedto indicate the true weight of extract in 36

Year Beer Malt Hops Sugar

1643 Introduced1660 Charged on

‘strong’ and‘small’ beer

1697 Introduced1711 Introduced1830 Beer duty

repealed1847 Use allowed

and dutied1863 Repealed1880 Re-introduced

based on standard‘original gravity’of 1057 Repealed Duty repealed

1889 Standard changedto 1055

1993 Changed to ‘endproduct’ dutybased on % alcoholat point of sale

Table 2. Summary of excise duty in the English brewing industry.


gallons, Quin, Richardson, and Dring andFage who all adopted Richardson's lb/brlnotation. In Scotland, Allan's saccharom-eter was in use. This was calibrated inounces per cubic foot, assuming, slightlyinaccurately that a cubic foot of watercontained 1000 ounces, thus giving areading similar specific gravity.

Figure 11. Dring & Fage slide rule for use withsaccharometer (Actual size 335 x 45 mm)

Figure 10. Dring & Fage saccharometer (AfterAccum14). Scale b range - 20lb/brl, divisions -0.2 lb/brl. Weights 1 or 2 added at 20 or 40lb/brl.


Accum considers that Dring and Fage wasthe preferred instrument of the town brew-ers at this time and describes both it andits accompanying slide rule (Figs. 10-12).

The saccharometer has a square stemand is weighted from the top. The firstside of the stem is calibrated 0-20lb foruse without a weight. Side 2 runs from20-40lb with weight 1 on top and side 3runs from 40-60lb with weight 2 on top.The open frame slide rule is made of box-wood with a short ivory slide with a tem-perature scale. The four face of the stockmarked ABCD provide continuous, butoverlapping scales for five parameters.The innermost scale (Density) givesRichardson's lb/brl. The second scale (D.Ex. Pr. Cent) gives the lb dry extract con-tained in 100 lb of wort. The third scale(D. Ex. Pr. Barl) gives the lb dry extract ina barrel of wort. The fourth scale (ProofSpt. Pr. Ct) gives the number of wine gal-lons of proof spirit that can be obtainedfrom 100 wine gallons of wort at theappropriate density (lb/brl). The fifth, out-

Figure 12. Scales detail to Figure 11.

Figure 13. Bate’s 5-poise saccharometer in ‘spectacles case’ (thermometer missing).


ermost line (Specific Grav.) gives theequivalent specific gravity.

Excise ambivalence to the duty on beerdid not extend to the distilleries ofScotland where duty was being paid onthe malt, the wort (or wash) and the spir-it and an Act of 1816 specified Allan'ssaccharometer as the instrument to beused to assess wort strength.

Here we must return to Bate. As AnitaMcConnell describes,8 in 1821 theEnglish Board of Excise ordered 80 Allansaccharometers through their officialsupplier Bate, who was anxious to obtainthe same monopoly for saccharometersas he had for hydrometers. Bate dis-patched one of his journeymen toEdinburgh who took all of Allan's men toan alehouse and kept them intoxicatedfor nearly a fortnight and then had themcarried to London by boat. Deprived ofhis workforce Allan's order was muchdelayed and although completed, Batehad used the opportunity to persuade theExcise into adopting his own instrument.Bates' saccharometer replaced Allan's inIreland in 1823, in Scotland in 1825 andwas legalised in England in 1826.

Bates saccharometer (Figs. 13 & 14)was usually made of gilt brass. Theupper graduated stem covers 30degrees of specific gravity and thelower stem ends in a loop which holds arange of weights (or poises) eachincreasing the range by 30deg. Theinstrument takes two forms: a brewer'ssaccharometer covering the range1.000 to 1.150 and a distiller's saccha-rometer covering the range 0.970 to1.150.

Tizard15 writing in 1850 considered thatBate's improvement on his predeces-sors ‘consisted chiefly of having 5 pois-es instead of Allan's 13 … and the abo-lition of the sliding rule, for which hesubstitutes tables for practical men.’

Tizard goes on to commend the work ofJoseph Long in producing a simple andelegant saccharometer scaled in lb/brland using only one poise. He alsomeets Tizard's approval by ‘his mode ofapplying his thermometer and saccha-rometer side by side, by which correctresults are at once given without callingin the aid of the sliding rule in the com-mon routine of business.’

Figure 14. Bate’s saccharometer with poise.


The firm of W.R. Loftus seems to havebeen in the business of making andsupplying copies of all the main types ofmeasuring equipment at this time. Loftus'catalogue diagram of a Long type sac-charometer and thermometer is shown inFig. 15. A later model with conventionalthermometer is shown in Fig. 16. Long is

credited also with the re-introduction ofan open frame slide rule. A Loftus copy isshown in Fig. 17. On one side anextended scale on both stocks allows fortemperature correction and also conver-sion from lb/brl to true lb dry extract/brl.On he reverse side the upper stock corre-lates wort strength in lb/brl with barrels

Figure 15. Loftus catalogue 1866. New improved saccharometer with single poise. Suppliedwith slide rule, thermometer with saccharometer temperature corrector and instructions.

Figure 16. Loftus single-poise saccharometer (specific gravity version).


brewed, the lower stock has a shillingsper quarter scale for estimating the com-mercial value of malt against the strengthof the brew.

Loftus' catalogue of 1866 (Fig. 18) sug-gests that the newer saccharometers con-tinued to compete with a range of the olderinstruments for many years. ‘Blind’ ther-mometers and saccharometers wereavailable also for process work so that thebrewer could engrave his own scale for hisworkmen, preventing them from revealinghis recipes.

As shown already, in Table 2, beer dutywas re-introduced in 1880. This was basedon the specific gravity of the wort, termedthe original gravity, converted to a notionalvolume at a standard 57 and later 55degrees. Over the next 40 years officialtables and methods of analysis weredeveloped by which the reduction of spe-cific gravity, or quantity of alcohol formed,during fermentation, were converted into‘degrees lost’ to calculate the original spe-cific gravity of the wort. As with spirits,these calculations were always performedwith the use of tables and the slide rulenever developed as a specific tool associ-ated with beer duty payment. Bates sac-charometer, often termed ‘the revenuesaccharometer,’ continued as the Excisereference instrument for specific gravitydetermination and by now it was beingmade by a range of instrument makers.Such instruments were available commer-cially but always subservient to the Exciseman's own instrument which he guardedwith some care. As the Commissioners

Figure 17. Loftus Brewers’ slide rule foruse with saccharometer.


ordered, ‘The hydrometers and saccha-rometers are to be kept locked up whennot in use, and upon no pretext whatevermust any of them be suffered to pass, evenmomentarily, into the hands of a trader orhis servants Any neglect of this injunctionwill be visited with the extreme displeasureof the Board.’ In practical terms Batesinstrument was supplemented with a rangeof simple metal and glass hydrometers

especially where the range of specificgravities to be measured was limited andpredictable.

Within many breweries tradition was hardto break. Joseph Long's catalogue contin-ued to offer a version of Richardson sac-charometer as late as 1932, possibly withreason, since it must have been easier tochange dry weights at the top of the stem

Figure 18. Loftus’ list of saccharometers for sale 1866.


rather than the Sikes/Bates instrumentswhich required removal from the liquid foreach change. The use of the brewers'pound continued for process measure-ments and both specific gravity and brew-ers pounds were recorded alongside ofeach other into the 1950's. Overall, brew-ing textbooks and journals show little inter-est in the use of the slide rule. In the caseof hydrometry this may be associated withhigh duty rates and the need to agreeexact figures with Customs and Excise.

In 1905 the Birmingham brewers met tohear a paper on The Development of theSlide Rule with some Examples of its usein the Brewery.16 In a two-edged discus-sion following the paper William WatersButler of Mitchell's and Butler's consideredthat they would not all rush out to buy aslide rule although the paper was a revela-tion to the possibilities of the slide rule inthe brewing room. Brewers had too muchclerical work ‘they did not want to be cast-ing out nines when they should be castingthe coppers.’ Another contributor did notthink that they need bother calculating thewages per hour - ‘the workmen did it gen-erally for them and nearly always got itcorrect’ and ‘however the standard workon the subject appeared to be The SlideRule by Charles Hoare, C.E.’

This article first appeared in theProceedings of the 11th Internationalmeeting of Slide Rule Collectors, 2005,and is reproduced with kind permission ofthe UK Slide Rule Circle.

References

1. Philosophical Transactions of the RoyalSociety, 1675, 329

2. Hopp, P., (1999) Proceedings of theFifth International Meeting of Slide RuleCollectors, Cambridge, 13-32

3. Scarisbrick, J., (1898) Spirit Assaying,Revenue Series No 3, 2nd Edition.

4. Tate, F.G.H., (1930) Alcoholometry,H.M.S.O.

5. Ashworth, W.J., (2003) Customs andExcise Trade, Production and Consumptionin England 1640-1845, O.U.P.

6. Philosophical Transactions of the RoyalSociety, 1730, 277

7. Boyle, P., (1800) The Publican andSpirit Dealers' Daily Companion, 5th Edition.

8. McConnell, A., (1993) ‘R.B. Bate of thePoultry 1782-1847,’ Scientific InstrumentSociety

9. Richardson, J., (1784) Statistical esti-mates with the Saccharometer

10. Reddington, W., via Mathias, P., (1959)The Brewing Industry in England 1700-1830, Cambridge University Press

11. Baverstock, J.H., (1826) Treatises onBrewing

12. Baverstock, J., (1785) HydrometricalObservations and Experiments in theBrewery

13. Booth, D., (1830) The Art of Brewing14. Accum, F., (1820) A Treatise on the Art

of Brewing15. Tizard, W.L., (1850) The Theory and

Practice of Brewing, 3rd Edition16. Lones, P.M., (1905) Journal of the

Institute of Brewing, 531-561

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