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DaveTooner
04-21-2002, 06:14 PM
Is it okay to use this kind of varnish in a medium? I have a bottle that says the ingredients are cyclohexanone resin, acrylic resin, and mineral spirits.

Thanks,

Dave
www.crewstoons.cjb.net

Einion
04-21-2002, 09:41 PM
Dave, polycyclohexanone resins are one of the better classes of synthetic resins in terms of optical characteristics and they have low viscosity which should mean the medium will have a tendency to level out (which of course a varnish would be designed to do so that it does not easily show brushmarks). Acrylic resins have relatively poor refractive indices and I imagine they would select one which would also level well. At a guess, the acrylic in the mix is there to act as a plasticiser in the dry film as polycyclohexanones get very brittle with age.

If you care about longevity I would do at least some long-term testing before using it extensively. Compared to mediums containing natural soft resins it won't quite match their optical properties but it will likely have other advantages: yellowing less and becoming insoluble over time, as oil films should be ideally (which, paradoxically, means it probably isn't suitable as a varnish!) Try a test with some paint and see how it goes; it should work fairly well optically, giving at least reasonable depth, and it might have beneficial handling characteristics. It should also dry quickly because the PCH resins are fast oxidisers.

Einion

DaveTooner
04-22-2002, 03:15 PM
Thanks. You sure know your synthetic resins.

Einion
04-22-2002, 07:26 PM
Yep, I can look up reference books with the best of 'em :D