I read somewhere that masonry dye can be used to color hydrocal (for rocks etc) so that they have a consistent color all the way through (don’t show white if chipped or cut). I have tried it but the hydrocal dries crumbly like it can’t set properly. Can anyone help? I searched the forums but couldn’t find the topic.
Thanks!
I used the Woodland Scenics product. It came out all right, but I had to use a lot more than I would have thought. The WS stuff is a liquid, and comes in a small container.
Did you do a “controlled experiment” with the Hydrocal, mixing one batch without the dye and one with it? I ask this because I’ve found that Hydrocal has a shelf life if you don’t keep it covered up very carefully. I buy 8 pound containers of Hydrocal from Scenic Express. When I got down to the bottom of the container, which took several years, I found that my castings came out crumbly. A fresh container solved the problem.
I mixed some india ink or acrylic paints to color the hydrocal. Works fine but you have to measure amounts if you want to make duplicate batches. Try a little to see what color/density you need.
-Bob
The Apple Barrel acrylic craft paints from Wal-mart, Hobby Lobby, etc. can be used to pre-color hydrocal, but don’t ever try plain household latex paint because a chemical reaction will cause it to set before you can even remove the spoon
Powdered masonry dyes should have no affect on the overall properties of Hydrocal or any other plaster. I use it all the time to “base” color Hydrocal for castings. Colored hydrocal is used extensively on our club layout for rock castings, retaining walls, abutments, roads and concrete foundations. You need to experiment to get a feel to the amount to add. Generally, adding the dye to the dry plaster will be quite close to the final dried/ cured product. I will always add dry colored plaster to water for a better mix, you just need to get a feel for the amount of water. You can mix far more colored plaster and just bag it for future use (Baggies and twist ties are great for storage to keep moisture from the plaster. I buy Hydrocal in 99# bags and break up into smaller quantities. I bag plaster into separate project sized bags and store in a sealable 5 gal pail. Old or improperly stored plasters will absorb a considerable amout of moisture and will affect it’s properties. Not sure if this was an issue w/ your castings or the type/ amount of coloring.
Paints and Sacrete liquid coloring will work, but I have found inconsistancies in color and problems w/ curing if far too much is used. Many use it for light coloring and have no troubles, I still like the “masonry” dye. Masonry suppliers will usually stock black, brown and brick red. Other various colors are also available but generally not stocked.
Thanks for all the tips. I did make a couple of small undyed “rocks” with the same batch of hydrocal which came out ok, but it was all from a partially used box (the milk-carton type) that had been open for quite a while. The larger peices were the ones I dyed and didn’t turn out. I’ll try again with fresh hydrocal. Do I replace the water with the same amount of dye or should the ratio be different?
With a powdered dye, you add the powder to dry plaster. Spoon in the dye and mix, keep track of the approximate amount of each. I will use a coffee can, and add color. The color of that dry mix will be quite close once dry. If you try to place the dye in the water, you will have no real idea as to the final color as the small bit of dye will be quite dark. Think of tile grout, you can color the plaster to any variation using black, brown or the brick red. Experiment and keep a record to reproduce the batch. I have done many rock castings that the final coloring was quite close to the desired finish. Washes and drybrushing to show variation was all that was needed.
The castings over the modified WS portal were done w/ dyed Hydrocal (iron black and a touch of brown), needed to add dark washes to show detail and drybrushed rust, greens and light tan on tips to show highlights
Abutment/ wingwalls formed and poured w/ colored plaster
[URL=http://s151.photobucket.com/user/bogp40/media/train%20club/trainclub2041.jpg.html][IMG]http://i151.photobucket.com/albums
Great pictures! Inspiring!! This will keep me busy for awhile - I can hardly wait. It has been a lot of help! Thanks.
Does anyone know if the Vallejo pigment powders can be used to color Hydrocal?
Just used some brown concrete pigment mixed in DuraBond (45min). A little goes a looong way, and at first, it looked like the cows got out and had their way on the countryside, but is literally drying boxcar red. It’s to be seen if I will have issues with paint “bleeding”, but will find out in a couple days
