I've long avoided gilding, partly because I love calligraphy best, partly because of the esoteric ingredients list. Slaked plaster is just the start of the weird-ass stuff you have to collect to create true gesso, that creates raised gilding.
In my long-term avoidance, I've collected every other imaginable form of glue (gum arabic, gilder's malt, gilder's milk from Oriane, improved body size, acrylic gesso, white glue, and most recently miniatum), putting off the inevitable. You want something sticky? I got it (ok except hide and rabbit skin glue, but I got fish glue).
No matter: I'm determined to 'get' this stupid gilding thing, or at least have a go.
So I order my dental plaster - costs more in shipping than in materials, and probably have three lifetimes supply.
Can I find distilled water, anywhere, in this world capital, in any
of its myriad shops, chemists, pharmacies? Of course not. Apparently it no longer exists, having given over shelf life to Bach remedies and aromatherapy.
You can get 'purified' water (not sterile, no explanation of how it's purified, but about £5/5L), you can get de-ionised water for same price, smaller quantities.
But distilled? no go. Apparently noone does ironing anymore, nor are there wet-cell batteries.
I have some purified water left from previous search (where I gave up and settled for purified H2O for mixing gouache), so I set up to test out a 30-min slaking process
(also required Ph strips, which no pharmacy I can reach stocks either - one staffer in a pharmacy suggested a stationery store. Hunh? Thank goodness for eBay).
AFAICT, though, I've failed...and instructions lie like a cheap rug. 30 mins? Um, no.
The instructions are to basically to start with high-quality plaster (Cennini's month-long soak is to remove impurities in part); soak the plaster in more water than it needs, keep stirring to keep it from setting, drain off excess periodically, and add more water, repeat 2-3 times, til Ph shows neutral, same as original water (which you checked).
Being concerned not to run out of my purified water, and not wanting to overflow my bowl either, I think I skimped on the first 'wash' of plaster, and as a result I now have not one but two containers of soggy plaster mix that won't set. And almost no purified water left.
Not a rousing success. Read a lot about Ph over the day, the dangers of distilled water (don't drink it, unless you're being poisoned - really); and now have plaster sludge to dispose of, somehow. Argh.
ETA (20 December): adding the 30-day challenge tag to this entry, as a prologue to my project. This was my first attempt at gesso.