(meteorobs) OT -Technical question on Hemispherical Mirror Undercoating.

[stange]

I have a concern with heat transfer & any acidic action of SPAR Varnish 
followed by a coat of Krylon Ultra-Flat Black paint on the underside(inside) 
surface of a hemispherical mirror which does not appear to be metallic.

Objective is to remove trace light leaks which will be evident with a very 
sensitive low light camera and still allow good (internal) heat transfer to 
mirror dome surface to counter dewing.

Anyone with experience in adverse effects of having done this?

Physical science & Chemistry input appreciated for the IR blocking system we 
have developed.

Thankyou.
YCSentinel