On Dec 15, 12:24*am, "N_Cook" wrote:

[about filter plate on high intensity lights]

I think you're right. I'd forgotten about waterglass. Once you make a
purchase under the lamp cover disc it comes away fairly easily. I did not
realise that waterglass can tolerate such high temperatures -

Isn't waterglass brittle and corrosive (etching the glass as it
adheres)?
I think a flexible high temperature adhesive like RTV silicone
is a better prospect, and more likely.

Dichroic reflectors and UV or 'heat absorbing' glass are typically
used on projector lamps which get quite hot, the thermal
cycling would fracture a hard adhesive.