Glass thickness

Carolyn Lamb <carolynpaintingconservator [at] rocketmail__com> writes

>I have to glaze a number of larger paintings including three quarter
>and full length portraits which will be on display in a public
>building. Does anyone have a rule of thumb or know of any
>information about when to move from one thickness to another based
>on size of the work?. There are standards for glass thickness in
>public buildings but these do not include glass on paintings.

There does not appear to be anything published which directly
applies to picture frames. I carried out some research into this and
can share some useful information I came up with;

I was concerned about large glazed paintings displayed in areas used
by the general public and looked into possible legal requirements.

There is no law requiring the use of laminated glass specifically in
picture frames,  but what does appear to be a legal requirement is
that any glass of a width greater than 250mm and on display below a
height of 1500mm  is required to be laminated by Building
Regulations 1991.

As a rule of thumb we glaze any paintings over 1 metre squared with
laminated glass.This seems to make sense for H& S reasons for the
protection of the painting and the handler and  is standard practice
carried out in other conservation departments such as the Tate
Gallery.

Rankins (glass suppliers, London) recommend the following
thicknesses: From 1000mm - 1500mm  glass should be 4.4mm laminated
and anything above 1500mm glass should be 6.6mm laminated.

I use 3mm  for anything up to 500mm and 4mm un laminated glass for
anything between 500mm and 1000mm. Unlaminated glass is usually
taped with low tack tape for transportation.

Our glass of choice is LUXAR low reflective glass.

With the larger paintings the joints in the frame often have to be
strengthened with metal straps attached over the joint. Additionally
metal 'L' shaped fixings are attached to the wall for displaying the
painting to support the additional weight

The maximum size available for low reflective laminated glass is
1900 x 3000mm. Paintings larger than this are glazed with perspex.

There is a low reflective perspex available from Optium Acrylic
products (Tru Vue)

There is a little more information on glazing at the V&A in the
following:

    C. Powell and Z. Allen.
    Preventive conservation framing: current procedures used for
    framing paintings at the V&A, The Picture restorer, No 29 Spring
    2006

Zoe Allen
Senior Frames and Furniture Conservation
Conservation Department
Victoria and Albert Museum
London SW7 2RL
+44 20 7942 2104
Fax: 44 207 942 2092


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                  Conservation DistList Instance 24:3
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