I got a couple questions for those that have used both the hydrocal and plaster of paris.
I picked up some hydrocal when I was down in Niagara, I never tried it before , I have always used the POP on the layout because it was all I could get in town here. I’ve used it for making castings from the woodland scenic molds as well as for adding strength and texture for mountains/hills, and have had very good results. So what I’m wandering is would the hydrocal be better for mold casts compared to adding to plaster cloth for adding strength and texture .
Another question is how do you mix the hydrocal for making rock castings?[:I]
Hydrocal is sets up very hard–no crumbling. It is very good for making castings. I mix it about the same thickness as pancake batter. The only problem with it is it sets quite quickly so if you are using it for basic scenery you have to work fast. For this I mix it a lot thinner & brush it on tulle to make my first layer. Hope this is understandable.I read some where if you mix in a little vinegar it slows down the setting time. When making a casting(rubber mold) hold it in your hand. When you feel it getting warm slap it in place over prewetted plaster.
This subject came up in a querry in the old “Clinic” feature of model railroader back in the mid-60s. It was when Linn Westcott was ardently promoting Hydrocal(R) and hardshell scenery. The main drawback, if I remember things, was plaster of paris’s weight; Hydrocal(R) could be “formed” into thinner sheets than plaster of paris thereby cutting down on the weight of the “hardshell”. It also tends to be a bit more brittle than Hydrocal and, therefore, a little more difficult to carve.
In earlier days plaster of paris was used over screen support for scenery; it is probably more readily available in smaller communities than Hydrocal(R) and can be used for “hardshell” scenery, greater weight and all. Just how Hydrocal(R) molds will adhere to a plaster of paris surface I don’t know having begun my experience with this hobby about the same time as Hydrocal(R) and hardshell scenery,
Lynn, the next time you’re in chat on site, ask Bob about it. He’s been using it for better than 30 years for scenery as well as castings. He says it’s the best for scenery because it’s very hard, strong and light. I wouldn’t use plaster of paris, because of the critter factor. It’s a fact that bugs love it. It may not happen right away, but if you use plaster of paris, you’ll have bugs sooner or later. If you can get hydrocal, I’d use it all the way. If someone says hydrocal isn’t good for scenery, either they’ve never used it, or they’re doing it wrong. Ask Bob.
Thanks guys for the info , I think the hydrocal will work well then in these new shallower bragdon molds I got , although I have darryl Huffmans videos and he used the same molds with plaster of paris without a problem. So I guess I’ll experiment with both for base coat and molds. The last layout, the mountains were built to withstand an earthquake and was made up of plaster of paris with screening.
I didn’t actually watch it, sorry. I just assumed they’d tell you how to mix it. Here are the instructions from mine: Use clean bowl and utensils. Do not wash product down drain. 1. Shake box (bag) gently for 30 seconds 2. Slowly add 1 1/4 cups Hydrocal to 1/2 cup water, mix. 3. Immediately pour into molds or brush on terrain surface. Working Time: 5 minutes Setting Time: 40 minutes. Overnight for complete cure. Warning: Do not take internally (I know, you’re tempted, aren’t you?). Keep out of reach of children (how are they going to learn?). Do not make body casts as Hydrocal may develop sufficient heat to cause burns if it is allowed to harden in contact with skin. (And you thought you could save on medical treatment by giving yourself a cast when you broke your arm!). Good luck.
I find it easier to make a bunch of molds and then attach them when they are dry using the “brick” method, only because I was sure I’d screw it up if I stuck it on while it was still wet. But I’m going to try it wet one of these days and see how that works. The advantage of doing it wet is that it should stick itself to most surfaces, including any plaster cloth without any problem.
I’ve attached the plaster of paris woodland scenic molds while they were soft , not wet there actually warm when there ready to attach and if you bend them a bit you can see that they will have a semi firm texture and crack a bit , meaning time to attach. Oh yes you have to make sure you give the area your attaching to a good wet down with wet water ( drop of soap to the water ).
I’ve also attached the molds when there hard when I’d attach them I would give them a good press to fracture them this gave a realistic effect.
Here’s a pic of a mountain face from the old layout , I’m not sure if you can see the fracrures or not but it gives you the idea
I can only relate my limited experience, but here it is: PoP is easy to use, and I found it to be a decent product for molding and that is about it. I found Hydrocal to be very difficult to mix…takes forever…but it also sets up much more quickly than the PoP. So, once again, PoP was great to cast rocks, but I used the Hydrocal to anchor them, and to generally create rock faces and cuts, and finally to create footing soil by building it up at the footings and sills of bents. Sculptamold would have done well for that, but I didn’t want to buy it without a good run at the first two products.
Differences that counted: four times the mixing for Hydrocal, and reeeeaaaallyy fast set-up compared to plaster. My guess would be, since I haven’t actually tested it, that the PoP would withstand less stress than Hydrocal.
I usually mix hydrocal with patching plaster (2 to1) to give it a little more working time and I also add about a tablespoon of water putty to the mix. Most of the time my hardshell consists of that mix over blue or pink insulating foam then paint or other coloring and ground cover over that .