I've had a few queries recently as to whether it was possible to colour my plaster letters. It is - they do pretty well with a coat of plain acrylic paint, in which case you can match them to your wall colour if you want.
However, one of the things I really like about casting these letters in white plaster is that the original letter I hand-carved was from white plaster. It had that lovely matte finish and the dry texture of the surface really appealed to me. So, in casting a letter that was originally in white plaster, with white plaster, I get a recreation of that beautiful original matte surface, which I love. Painting over it seems to be a shame, to me.
So, I looked at how I could colour the plaster mix itself - maybe I could retain the dry-looking matte surface?
Here, I tried adding black Indian ink to the water that I mix with the dry resin plaster. I used a very strong mix (one part ink to three parts water) and as a result the plaster took well over 24 hours to set hard - normally it's ready for demoulding in less than an hour. It also stuck pretty fiercely to the mould (even though I'd talc-ed it well beforehand) and left pieces of itself behind - not a success.
Then I thought 'well, if that's not going to work, perhaps I can soak a letter in the ink, neat.' and after a 24-hour bath, this was the result.
A grey, rather than black outcome. It has a great concrete-y industrial look that may work really nicely. However, in playing with the Indian ink, I noticed something a bit gross about it. It stinks. I mean, it reeks, and I'm afraid the vomity pong lingers in the cast result, even after a very good scrub and a long sit in the sun!
Then I tried a product that was designed to do approximately what I'm trying to achieve - concrete colourant. It's used to colour grout, too, so I figured it was bound to work. I did have to add way more water than usual to make the plaster wet enough to cast, so I don't really know the correct water/colourant ratio. It did set in a reasonable time though, but most importantly - it has that dry matte finish that I like so much. Hoorah!
The only downside I discovered was that in scrubbing off the talc under the tap after demoulding, I got black all over my hands, which means that the colourant isn't waterproof. This surprised me, as it's designed for grout, and surely it would be used in wet areas? This isn't really a problem as I don't recommend installing these plaster letters where they'll get wet - it's more of a production challenge.
What do you think? Should I try a production run?