Glass expansion question and anyone know this moulding

[Gemmie123]

Hi there
Couple of questions ….
Is there a standard expansion gap that should be left for glass in a frame and it should be a larger gap for acrylic glass right ?

Does anyone recognise this moulding ?
(Sorry for the rubbish photos they are screenshots from a quick reel )

Thanks in advance

[prospero]

Glass expansion is not really an issue. The reason for leaving a gap is more to do with the transfer of shocks to the edge of the frame
going through to the glass. If it's tight then there is more a risk of cracking.
With plexiglass there is a problem with expansion. The bigger the sheet the more generous the gap.

[Gemmie123]

Thanks

[Justintime]

There have been a few data sheets posted on other sites for acrylic expansion. From memory for a "standard" size the usual 2-3mm gap all round is fine, but for large/oversized pieces the gap needed went up to 4-5mm all round!