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LightCheck® light monitoring dosimeters From the laboratory to the museum
A.-L. Dupont Centre de Recherche sur la Conservation des Collections, National Natural History Museum, ParisP. Menino HomemFaculdade de Letras da Universidade do Porto
SUPP-CZ
COST D42 – Workshop SHOWCASES INSIDE OUTMay 24th-26th 2009
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LiDo “A Light Dosimeter for Monitoring Cultural Heritage:Development, Testing and Transfer to Market
(FP 5 2001 – 2004)
Tapestry of the Apocalypse, Angers (photo LRMH)Front Back
LightCheck® Sensitive
LightCheck® Ultra
Effect of light exposure on artefacts…
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LCS and LCU
LightCheck® Sensitive LCSblue dye - Ormocer® / glassProgressive bleaching blue / white
Fraunhofer (ISC)
LightCheck® Ultra LCU(blue + red) dyes + additives - PVAc / paperProgressive change blue / purple / pink / white
CNRS (CRCC)
LD
LD
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Dose-Response FunctionLightCheck®U & LightCheck®S vs. BWS no.1
L um inous exposure [kluxh]0 100 200 300 400 500 600
Col
our c
hang
e∆ E
0
10
20
30
40
50LC U LC SBW S 1
To obtain a total colour variation
∆E ≅ 10-12the exposure needed is
12 klx.h for LCU
60 klx.h for LCS
250 klx.h for BWS1Ex. 50 lx: LCU 30 days, LCS 150 days, BSW1 625 days
LCU
BWS 1LCS
Curves obtained with controlled light-ageing (500 lx QTH, T=23°C, 50% rH)
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light-sensitivity
BWS BWS -- LCS LCS -- LCU LCU Low exposure levels, not detectable with BWS are detectable with LightCheck®
LightCheck®U and LightCheck®S have different and complementary operational ranges
Very-light sensitive, fugitive objects
Short exposure periods
More durable objects
Longer exposure periods
LCU 0 to 100 klxh
LCS 60 to 400 klxh
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Influence of light source / illuminance
LightCheck®U
Similar behaviour with- QTH (40 – 500 lx)- Natural (no direct sunlight)- Simultaneous multiple sources
Different behaviour with- 100% fluorescent light- metal halide
Some characteristics of LC
0
10
20
30
40
50
60
0 20 000 40 000 60 000 80 000 100 000 120 000LD (lx h)
DE
500 lux halogen5000 lux fluonatural light (avg 100 lx)mixed natural+halogen+fluo (avg 300 lux)in-field halo exp (avg 40 lux)Servathin 193 klx
∆E*
LCU
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Influence of other environmental parameters:temperature / rH
05
101520253035404550
0 20 000 40 000 60 000 80 000 100 000LD (lx h)
Del
ta E
DE* 40 C-50% rHDE* 30 C-50% rHDE* 25 C-50% rHDE* 20 C-50% rH
05
101520253035404550
0 20 000 40 000 60 000 80 000 100 000LD (lx h)
Del
ta E
DE* 20 C-70% rH
DE* 20 C-50% rH
DE* 20 C-30% rH
∆E
∆E
rH variation: no influence on fading T raise: increase in fading rate and saturation threshold
LightCheck®U
LightCheck®SrH raise: increase in fading rate and
saturation thresholdT raise: increase in fading rate and
saturation threshold
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From laboratory tests to calibration
LightCheck® integrates the light effects with a cooperative action of other environmental parameters
choice for calibration: Reference Colour Scale with few colour steps to take into account the variability due to the environment but also to account for the subjectivity involved in the colour evaluation (observer dependent)
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Reference Calibration Scales (RCS)
0S
1S
2S
3S
4S
4U
3U
2U
1U
0U
LCU Equivalent luminousexposure (lux hours)
0U 0 - 5 000
1U 5 000 - 30 000
2U 30 000 - 45 000
3U 45 000 - 75 000
4U 75 000 - 100 000
LCS Equivalent luminousexposure (lux hours)
0S Below 60 000
1S 60 000 - 100 000
2S 80 000 - 240 000
3S 200 000 - 340 000
4S Above 340 000
LightCheck®S
LightCheck®U
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In-situ exposures
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In-situ exposures
Investigation of different aspects:
• Simultaneous exposure of LightCheck® prototypes and Blue Wool Standards with monitoring of illuminance, T and rH (ELSEC IrLog data-loggers)
• Corroborate laboratory experiments
• Suitability / limitations due to the respective operational ranges
• Use of the Reference Colour Scales for quantitative assessment of Light Dose
• Influence of seasonal / environmental variations
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Selected results – Uffizi Gallery, summer 2003
data-logger ELSEC
VIS light, UV, T, rH
LCUBWS1
LCS
“Maestà”, Giotto (c.1310)
Site 1. Giotto roomNo windows, 100% artificial lightStable lighting conditionsHighly frequented by public
Site 2. Geographic maps roomLarge windows with curtains, almost 100% natural lightwide illuminance fluctuationMost often closed to public
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Uffizi gallery - "Geographic maps" room
measurement time30 days 45 days 90 days
∆0
5
10
15
20
25
30
35
40
45
50
Geographic maps: Imean 100 lx - Imax 830 lxUVmean 6.4 mW/Lm (UVmax 42 mW/Lm) T 30°C (Tmin 27°C – Tmax 32°C)rH 60% (rHmin 42% - rHmax 90%)
LCU: saturation within 1st monthLCS: visible fading after 1st month(not reached saturation at 3rd month)BWS 1: visible fading after 3rd month
LCU
LCS
BWS1
Uffizi gallery - "Giotto" room
measurement time30 days 45 days 90 days
∆E
0
5
10
15
20
25
30
35
40
45
50LightCheck U LigthCheck SBWS 1
Giotto room: Imean 11 lx - Imax 50 lxUV 0 mW/LmT 28°C (Tmin 26°C – Tmax 29°C)rH 53% (rHmin 35% - rHmax 67%)
Selected results – Uffizi Gallery
LCU: visible variation 1st month(not reached saturation at 3rd month)LCS: visible fading at 3rd monthBWS 1: under threshold
LCU
LCS
BWS1
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In-situ exposures - LCU
LightCheckU
Luminous exposure [klux*h]
0 20 40 60 80 100 120 140
∆E
0
10
20
30
40
50
Prague (June 03) London (June 03) Florence (June 03)Calibration Artif light Ageing 500lux Halogen
Calibration curveQTH lamp, 500 lx23°C, 50% rH
LCUs exposed for one month (June 2003)
LD of in-situ samples monitored with IrLog data-logger
All data points obtained in-situfall on the standard colour variation path of LCU as calibrated in the laboratory
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In-situ exposures - LCS
Calibration curve QTH lamp, 500 lx; T=23°C, 50% rH
LD of in-situ samples monitored with IrLog data-logger
∆E obtained is equal or higher to that obtained in laboratory⇒ More severe damage occursthan expected on the basis of calibration under stable conditions
Integrating effect of the overall environment impact on the evolution of the indicator’s colour
0 100 200 300 400 500 600 7000
5
10
15
20
25
30
35
40
Calibration curve 500lux in labFlorence (3th Camp.). Paris (3th Camp.) Prague (3th Camp.). Florence (4th Camp.) Prague (4th Camp.) London (4th Camp.) Berlin (5th Camp.)
Luminous exposure [klx*h]
∆E
/ 13090
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End user’s experience
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LCU
Caim’s head. António Teixeira Lopes, 1866-1942
Sanguine. Facing artificial and natural light
The drawing has been chosen because:
a) It is signed by the artist and it has a great value;
b) It is considered as a very fragile and sensitive object;
c) The museum is planning a permanent exhibition and wants to assess the risk of damage if the drawing is placed near the north window.
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LCUStart date / end date: 11.02.2005 / 04.03.2005 (22 days)
Light exposure: Artificial and natural light. North window and skylight.
Climatic conditions: 13 - 18ºC / 36 - 66% rH
Mitigation measures: double window, with curtains. Artificial light is always off except during visits
Hours of light exposure: 8 h/day of natural light + avg 1 h/day of artificial light (visits and maintenance routine)
Luxmeter reading : average on one day (11.02.05) 173 lux
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LCU
hours of exposure: 8h/day; 56h/week
evaluation from colour chart: closest reading 2U = avg 35 000 lx.h [30 000 to 45 000] lx.h
= calculation dose / annual exposure in hours
173 lx × 56h/week = 9 688 lx.h/week
- 9 688 lx.h/week × 52 weeks = 503 776 lx.h/year (estimated from one punctual reading)
- 35 000 lx.h × 365 days / 22 days = 580 682 lx.h/year (estimated with LightCheck RCS) [497 727 – 746 591] lx.h/year
LCU Equivalent luminousexposure (lux hours)
0U 0 - 5 000
1U 5 000 - 30 000
2U 30 000 - 45 000
3U 45 000 - 75 000
4U 75 000 - 100 000
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LCS
Flowering apple trees. Silva Porto, 1850-1893
Oil painting. Facing artificial and natural light
This painting has been chosen because:
a) It was painted by Silva Porto, very important Portuguese artist who played a prominent role in the introduction of the Naturalism in Portugal. He was a personal friend of António TeixeiraLopes. The Collection has only three Silva Porto paintings, all very valuable. This is the most valuable one.
b) a CCTV security system was installed which lead to the decision of leaving the artificial light on during the night to enable the guard to see.
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LCS
Start date / end date: 30.11.2004 / 24.01.2004 (56 days)
Light exposure: Artificial and natural light. Facing south windows.
Climatic conditions: 12.5 – 18.9ºC / 36.5 – 69.5% rH
Mitigation measures : Double window, with curtains. Artificial light always off, except during visits… and night surveillance (!)
Hours of light exposure: 8 h/day of natural light + 11 h/day of artificial light (night period) + avg 1 h/day of artificial light (visits and maintenance routine)
Luxmeter reading: with natural light, the differences within one
day are very high
Difficult to choose a number(176 lux was chosen)
30.11.04Natural and artificial light
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LCS
hours of exposure: 20h/day; 140h/week
evaluation of the reading from colour chart: Between 3S and 4S, 340 000 lx.h
= calculation dose / annual exposure in hours
- 24 640 lx.h/week × 52 weeks = 1 281 280 lx.h/year (estimated from one punctual reading)
- 340 000 lx.h × 365 days / 56 days = 2 216 071 lx.h/year (estimated with LightCheck RCS)
LCS Equivalent luminousexposure (lux hours)
0S Below 60 000
1S 60 000 - 100 000
2S 80 000 - 240 000
3S 200 000 - 340 000
4S Above 340 000
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Comments made by the end-users
For LCS
Fading occurred faster than expected from the punctual luxmeter reading.
The hues of colours of the RCS do not really match the actual coloursdisplayed by the LCS, especially for stages 3S and 4S, which makes the reading and the assessment of the luminous exposure difficult.
For both LC
It was a very useful exercise, it equipped the team with friendly and innovative tools to assess and to “prove” damage
Helped in taking decisions about lighting conditions, think about strategies to mitigate light damage, ensuring a better preventive conservation policy.
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Thank you!
