Microfading Tester International Discussion Group

How are you applying microfader data to your lighting policy? What acceptable lifespan are you using and what assumptions do you build in?

Here at The National Galleries of Scotland, Edinburgh, UK, we are using light budget recommendations as seen in the table below.

We usually work to an acceptable lifespan of 500 years, as this works for the breadth of materials and age range that we have in our collection and the fact that part of our mission is to preserve our collection for the people of Scotland. We do have some works that have an acceptable lifespan of 250 years, and this is agreed to case by case. At that point we just scale the above table (assuming a linear relationship, which we accept, as this is all guidance).

The table above is based on 'high' and 'low' use, but that could also refer to significance. It is based on accepting 10 just notable differences in the object's lifespan. Lux hours are assumed and are accounted for in the maths behind the table, but not expressed in the table. Lux levels are based on 8 hours of exposure per day.

How are others expressing MFT-driven lighting policy for your organisation?

Hey Kirsten, the architectural quirks of our National Museum building mean that we have considerable variability between the display conditions, with some areas well managed and some areas allowing direct or uncontrolled sunlight at certain times of day/year. Accordingly, our general lighting guidelines are designed on a 'per-gallery' basis, with lux measurements taken at install, and active lux monitoring undertaken where necessary in uncontrolled spaces. Active lux monitoring has also been showing that, realistically, the 8hr/day averages we work to aren't always that accurate, which is one of the reasons we have been reviewing our guidelines every few years. I have attached our 2021 Lighting Guidelines with Significance, which is currently under review.

Our guidelines are based on those developed here by the wonderful Bruce Ford and our previous Conservation Manager Nicki Smith, which are well documented in their 2009 AICCM Bulletin article 'The development of a significance-based lighting framework at the National Museum of Australia'. Like yours, they are based around expectation of a 500-year lifespan, with 10 JNDs assumed to be end-of-usable-life for low-chroma colourants. I understand this criteria is informed by Derbyshire, Ashley-Smith & Pretzel's 2002 guidelines. 

With this said, the guidelines are designed to be used with, and adjusted according to, curatorial significance assessments, as well as an assessment made on the expected demand/enduring cultural relevance of the object, and also our own assessments of its expected material lifespan (considering other inherent vices, etc). Bruce has a few examples of his wonderful MFT reports on his website, which give a good sense how recommendations are applied based on the data--much of what I have written above is covered in his 'notes and references' pages. We developed our microfading capacity in view of reducing the burden of object changeovers, so we try to use the results to inform data-led increases to display periods, which most of the time we are able to do.

Hope this answers your questions... I know a lot of that info is already out there, so sorry if anything there isn't really that useful.

How are you applying microfader data to your lighting policy? What acceptable lifespan are you using and what assumptions do you build in?

Here at The National Galleries of Scotland, Edinburgh, UK, we are using light budget recommendations as seen in the table below.

We usually work to an acceptable lifespan of 500 years, as this works for the breadth of materials and age range that we have in our collection and the fact that part of our mission is to preserve our collection for the people of Scotland. We do have some works that have an acceptable lifespan of 250 years, and this is agreed to case by case. At that point we just scale the above table (assuming a linear relationship, which we accept, as this is all guidance).

The table above is based on 'high' and 'low' use, but that could also refer to significance. It is based on accepting 10 just notable differences in the object's lifespan. Lux hours are assumed and are accounted for in the maths behind the table, but not expressed in the table. Lux levels are based on 8 hours of exposure per day.

How are others expressing MFT-driven lighting policy for your organisation?