Glass thickness

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.

Commercial framers use 2mm but I never go under 3mm. Old float glass
is 6mm (1/4 inch) Currently I use 3mm for a painting up to 1 metre,
4mm when one dimension is around 1 metre or above, 4.4 laminated
when it is around 1.5 metres, and perspex when it gets very big. The
frames have to be substantial enough to take the glass weight and it
does depend on the shape.

I am never quite sure when to move from one thickness to the next so
welcome thoughts or any published information.


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