Using Asphaltum on Edison Phonographs

[keywindgem]

I have read a few articles but want an opinion of members here.
In painting the liquid Asphaltum on my Edison Home all I am doing is thinning it with Shellite (white spirit) and painting with a good fine bristle brush. It seems OK, nice finish and touch dry reasonably quick, then baked in the oven while the wife is out shopping
Some of the old Japanning recipes added all types of additives into the mixture, is using the thinned Asphaltum all I have to do.
How long does it take to fully cure and feel hard to touch so I can apply decals??
Peter