Enrichment · Passion Projects · Museums and collections

Light the show
without fading
the quilt.

Type the opening hours and each object’s light reading. The calculator adds up lux hours over the run, compares each object with its yearly limit, and tells you how dim or how short its time on view should be.

Check the exposureWhat you get

The light exposure calculator

The worked example is a made-up six-month local history exhibit. Nothing you type leaves this browser.

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What you get

Enrichment · Passion ProjectsFree

What you finish with
Each object’s lux hours for the run, the share of its yearly limit, its maximum weeks on view and the light level that fits the run, with objects over the limit flagged. It prints as a summary and downloads as a spreadsheet.
Who it is for
Students curating exhibitions, museum studies and art teachers, and volunteers at small museums, libraries and historical societies.
Format
Browser calculator for a phone, tablet or computer, by touch or keyboard. Prints a summary; downloads a spreadsheet (.csv); export and import a file.
Access
Free. No account, no sign-in and nothing to install. Everything you type stays in this browser; nothing is sent to Caveat.
Where it lives
The Passion Projects space in Caveat Enrichment.
Support
Questions, a correction or a request: team@caveatacademic.com.

How to use it

  1. Measure each object’s light level in lux at its surface.
  2. Choose how sensitive each object is to light.
  3. Type the lit hours, days a week and weeks on view.
  4. Read which objects go over their limit.
  5. Dim, shorten or rotate those objects and check again.

Check the exposure

How the exposure is counted

Light level times time, against a yearly budget.

The worked example: a quilt in a six-month history exhibitLit hours1248 h8 h × 6 days × 26 weeksExposure62,40050 lux × lit hoursLimit15,000high responsivity, a yearUsed416%the quilt in this runThe worked example: a quilt in a six-month history exhibitLit hours1248 h8 h × 6 days × 26 weeksExposure62,40050 lux × lit hoursLimit15,000high responsivity, a yearUsed416%the quilt in this run
Damage from light depends on dose, so a dim light for a long time does as much harm as a bright light for a short one.

Lux hours

Fading follows the total dose of light, called the reciprocity principle: 50 lux for 300 hours does about the same harm as 150 lux for 100 hours. Multiply the lux at the object by the hours the lights are on and you have its exposure. Ultraviolet adds damage per lux, so remove it first.

Sensitivity groups

The International Commission on Illumination (CIE 157) sorts materials by how quickly they respond. Highly responsive ones such as dyed textiles, watercolours, colour photographs and most paper have a budget of 15,000 lux hours a year; medium ones such as oil paintings 150,000; low ones such as some metals and stone 600,000. A conservator can place a specific object more exactly.

Sources

  1. Commission Internationale de l’Éclairage. CIE 157:2004, Control of Damage to Museum Objects by Optical Radiation (cie.co.at).
  2. Canadian Conservation Institute. Agent of deterioration: light, ultraviolet and infrared (canada.ca/en/conservation-institute).
  3. National Park Service. Museum Handbook, Part I, Chapter 4: Museum Collections Environment (nps.gov).
  4. Library of Congress. Preservation: care of exhibited materials (loc.gov/preservation).

The worked example is made up. Treat the sensitivity groups as a starting point; a conservator can assess a particular object. Your entries stay in this browser. Support: team@caveatacademic.com.