I sealed 15 miniatures yesterday with Games Workshop Purity Seal. While it went on clear, after about 20 minutes I got moderate frosting. You can see it clearly on the bases between the two bodgers. Fortunately,the figures I painted look OK a bit ‘dusty’ but this would be unacceptable on my entire army!

After some research I made two mistakes.

1. Sprayed aerosol varnish in high humidity and low temperature: Last night we had 80% humidity and high 50’s / low 60’s temperature in the garage. After reading through the application pages on Golden & Liquitex varnishes, they don’t recommend applying varnish below 60 degrees Fahrenheit.
2. Sprayed all figures at once: With aerosol cans, if you ‘spray longer’ the can/spray cools down rapidly. That will have lowered the temperature even more, lowering the dew point and allowing water vapor to form in the varnish and create the frost.

I plan on picking up some some Krylon satin varnish (aerosol) and some golden/liquitex matte/satin/gloss varnish (air brush) and experimenting (given that temp/humidity is decent)

UPDATE:
I applied a single coat of Krylon UV-Resistant Clear Matte Acrylic Coating over the frosted Games Workshop Purity Seal and it ‘erased’ the frosting experienced with the purity seal. While I can’t vouch for the durability of the krylon matte acrylic coating, it didn’t frost. Temp in the garage is roughly 65 degrees Fahrenheit and 67% relative humidity. Below the Bodger on the left has one coat of ‘frosted’ purity seal and one coat of the Krylon coating. The Bodger on the right has no varnish or finish of any kind. I think the more reddish hue of the bodger on the left was proably just a stronger Reaper ‘flesh’ wash and has nothing to do with the finish.