Help With Sealing Fake Rock With PVA

[..:: F1D0 ::..]

Ok, so i finally finished the painting of Helio's fake rock wall tonight and the sealing begins tomorrow after work. Anyway, i was about to pop out for some varnish and my neighbor who a few months back made a fake wall for his leos gave me a pretty much brand new 15L tub of PVA. now i know you can seal using this which is fine, however to what consistency? ive heard different things from pure pva to 1 part water, 2 parts pva, 1 part pva to 2 parts water a 50/50 split and im confused lol. Plus how do i get the "2 parts PVA 1 part water" im crap at maths and frations lol

Cheers