It looks like I can’t get Hydrocal locally (I could order it and pay the shipping) and the only plaster at the home stores is plaster of paris. What are the plusses and minus of the various products, in particular for casting roadways? Thanks.
I’ve used drywall mud (the pre-mixed variety) for roads, and, while it’s easy to use, the surface is very soft and easily damaged. Applied to a thickness of any consequence, it also takes a long time to dry and can shrink or crack if applied too thickly. I find that patching plaster is more suitable and also use it for my scenery contours, over screen. The brand which I use is called Durabond 90, made by Canada Gypsum, and it’s also made by U.S. Gypsum. The “90” in the name refers to the setting time in minutes and there are other setting times available. Because it contains a catalyst, it comes only as a dry powder in, I think, 1lb. and 5lb. boxes or 33 lb. bags. It should be available at most lumber yards, including the big box ones. It will set in the prescribed time, regardless of the consistency, although very watery mixes seem to lack strength. Properly mixed, and cured, it is very hard and not suitable for sanding or other surface finishing, so that type of work should be done after it has set but before it is fully hardened. It “works” much like drywall mud, using the same tools, and takes paints and stains fairly well. I’ve used it as a skim coat and in some areas over 1" thick, and in neither case does it shrink or crack. If you’re applying it over a porous surface, such as wood or plaster, pre-wet the surface beforehand - this prevents the surface from drawing too much water out of the plaster mix.
Road made with drywall mud:
Durabond roads:
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Duhrams water putty is good for stuff that needs more strength.
http://www.waterputty.com/
A little too pricey to make mountains with, but not bad for roads and castings. Doesn’t take stain as well as plaster though.
Where you live has a bearing on what you can use. On the west coast (Calif), most any hardware store carries a product called ‘Fixall’. It’s for patching and filling wood and is used for underlayment leveling and smoothing. It’s working time is about the same as casting plaster–bad thing is, it cures pinkish. Here in the Heartland, most ‘floor fillers’ are more of a cement product that cures dark gray and sands easily to a light gray. I personally prefer either of these products over drywall mud.
As for hydrocal, Google ‘United States Gypsum’ and search for a local dealer or call their 800 number. Chances are, you’ll have to buy a min 50 lb bag–about $12-$14.00. My only source is a concrete (Readymix) dealer who stocks a few plaster items. Be advised, when you get to USG or a dealer, they have several different products in the hydrocal/casting plaster family and they propably won’t be able to advise you on which one to buy. Good Luck, Steve
I’ve done most of my mold casting with Hydrocal. I think it’s lighter than Plaster of Paris. It does take paints and stains very well.
For roads, I also use Durham’s Water Putty. It’s a hardware-store item. It gives me a very durable surface. I use a wash of acrylic paint on it, which works for me.
I’ve been working on an area of my layout with Bragdon Foam casting. The process is more complicated than simple plaster castings, but the results are really very nice. www.bragdonent.com for more information on this stuff.
I use Easy Sand plaster from Sherwin Williams, because I always have lots of it on hand. You have to mix it up. It comes in 25LB bags for about $10. it also comes in 20min, 45 min, and 60 min set times.
I avoid the premixed drywall joint compounds, except for the crudest of tasks, it is too soft and cracks as it dries, I don’t think it holds up too well.
Hi!
As Hydrocal was either not available (readily) or too expensive, I’ve always used plaster of Paris. However, I learned that you can delay set time with the addition of vinegar (about 1 tablespoon to a pint or so - forgot the best ratio). Also, no matter what plaster like substance you use, I would add some pigment - either acrylic or latex color or Tempura dry color - so that if its drilled or chipped or cut, that striking “white” color will not show.
To go back to my youth in the '50s, I remember going to the corner hardware store (Chicago) to buy plaster of paris by the pound - and it was 5 cents per!!! I think the biggest amount I got at one time was 5 lbs for my Lionel layout.
ENJOY,
Mobilman44