Been making some wood patterns for some castings, but my tin of 'Pattern makers red' paint is nearly empty.... Can you still get hold of any now? Or do people just go for ordinary household wood paint these days ? I am not sure if there is any major difference..
Strictly speaking this is a coloured shellac spirit varnish, not a paint. The difference is that paint cures to form a surface skin, but shellac (bug juice dissolved in alcohol) simply dries out of solution. A shellac surface can thus be re-worked by further layers which will merge perfectly with the old surface (the key to french polishing).
I've not seen it for sale, but you can easily make your own. Get some cheap "button shellac" (from Screwfix or Axminster) and colour it with finely-milled (paint grade) red ochre (Liberon, from Axminster). Traditionally different colours (usually red or green) might have been used by different patternshops but black was also used to show where the core prints went.
Despite recommendations, don't use "Chinese vermillion" to colour your shellac. This stuff (mercury sulphide) is far too toxic to be using lightly. I'm not surprised to see it listed in my 1930s Machinery's Handbook, but I'm amazed to see that the 1980 edition still quotes it, word-for-word. I do still use vermillion in shellac, but only for repro woodworking, not for patternmaking.