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.

As a fairly frequent re-glazer of damaged taxidermy cases, I tend to
use 3mm glass much as you do but within slightly increased
parameters and move up to  4mm for cases larger than 1.5m always
assuming that the case frame can take the  increased weight.

I have occasionally found that free-standing cases, that are
vulnerable to being kicked, have been glazed with anything up to
20mm. For wall-mounted or stacked cases, these are normally within
the 3mm size range of case, so there is little problem. Earlier
cases (19th century to early 20th) are frequently glazed with 2mm,
occasionally with 1mm, where I suspect that the original taxidermist
was trying  to save money with cheaper glass.  Large sheets of 1mm
glass (but never over 1.5m yet) make me very nervous but seem to
have a slight flexion tolerance, even when over 100 years old.

I hope that this helps,

Simon Moore MIScT, FLS, ACR
Conservator of Natural  Sciences
20 Newbury Street
Whitchurch RG28 7DN


                                  ***
                  Conservation DistList Instance 24:3
                  Distributed: Wednesday, June 2, 2010
                        Message Id: cdl-24-3-004
                                  ***