Thanks to a comment from a very good artist friend of mine i just realised i did not explain fully why I chose the odd long drying period for my White Matter©
skulls i am painting. I do apologise most sincerely a simple oversight I shall now repair.
Plaster ‘pure’ plaster that is, is very absorbent when it comes to moisture be it small amounts in the air or a good down right soaking. Some people may think once you use plaster from the bag and it then cures fully that is the end of the story but no. Just because you activated the plaster so to speak then it dried out again does not mean it can not then continue to absorb moisture, it will.
Now that’s pure plaster be it the basic gypsum (dry walling) plaster form or the more refined white plaster of Paris (sculpting type) The only real difference is in the name not the end effect. Plaster in any state ‘will’ continue to absorb moisture when exposed to it. Ever tried hanging paper on a new plaster wall without painting it first? This is why you should always paint a new plaster wall before hanging paper to slow down the plaster sucking the moister from the wall paper paste too fast.
Now it is at this point I ask you to remember I only use water based paints (tempura type) even though I will be using extremely thin coats none the less I will be building up small amounts of water for the skulls to soak up. Now ordinarily a day or two air drying (no additional heat) for pure plaster would be more than sufficient for my skulls to soak up and dry out considering the amount of paint I will use on each one. More so as I am not painting these with a paint brush, I am using old sponges.
The reason I have decided to give the skulls a whole seven days to dry again before sealing is the tissue pulp content of the White Matter© medium I created even though it is a small amount is going to potentially cause the plaster content to hold the water slightly longer in either small pockets or small thin layers of pulp within the White Matter© medium. Once I seal them this could cause the paint to flake later. Using other paint types would more than likely have similar effects but probably over a longer time frame.
Okay why not simply radiator dry the skulls then some might be asking? Simply for the same reasons only several times faster which would more than likely cause minute cracking and potential weak points between the pulp and plaster in the medium that may not be visible especially under the paint. Add to the mix when you say to someone “These are ‘ornamental’ and not meant to be constantly handled” There is always going to be someone who comes along and goes “Oh look at this…” Picking up what was not meant to be.
It has always been a belief of mine that accidents don’t just ‘happen’ less someone gives them a reason to. More caution means less chance of a casualty so I prefer to lean more on the cautious side when I can.