Just a question to you all, I’m still in the teething stages of model railroading, (literally only got into it 6 months ago).
I just need to know how various plaster types differ from one another.
My father has a bag of Cornice plaster at his home, (unfortunately its original packaging have been long discarded so I can’t even read what type of plaster this is).
But on the instructions for my rock molds that I have its specifying Hydrocal plaster, and in my searches I have also found Hydrostone plaster, heck even dental plaster has been advertised along side the above, and of course I have seen Plaster of Paris for sale also. If anyone can give me a laymans explination of the plaster types, it would be greatly appreciated.
I am NO expert. I used some lightweight hydrocal plaster in my molds and it was good, also expensive. I use mostly Plaster of Paris in my molds, works good, but sets up fast so you have to be ready. I tried some Woodland Scenics plaster and it was wonderful, but way too expensive for my tastes.
Warning. Do NOT wash any plaster tools or left over plaster down any drain. It will cure and plug the drain. I have a 5 gallon pail I use to wash everything, and empty it and wash it outside every few months.
For top coating scenery I use premixed lite weight drywall seam compound. It works well and CAN be washed in a sink. It also takes a day to dry and thus is easier to work and carve. I also use this for my version of ground goop (1/3 compound, 1/3 house paint, 1/3 sawdust and a teaspoon of lysol) I do vary the ratios to get different consistancies. I sometimes use artist acrylic colors and water instead of house paint to get special colors.
I hope this gets you started. More specific questions will get aditional information.
Hydrocal is a preffered product but not essential. It is used becasue it drys very hard and is much more durable. That said I have never used it and just buy a 50 # bag of whatever is cheapest at Home Depot or equivalent and cast away. You may find you break some extracting them but so what. they are cheap and you can use them in other locations. Also if you make a subterrain with plaster saoked paper towels to glue the casting to you can spray the subterrain with water, fill your mold and stick it in place. Then it is easier to remove the mold after it has reached enough drying time to do so.
If you want to use if for molds, you needn’t worry about set-up time quite as much as you would for where you intend to do free-hand carving, such as when creating rock cuts, natural tunnel portals, and rock faces. I always use simple Plaster of Paris in my rubber molds. It should be like thick cream in consistency, and you can pour it directly into a mold that has been pre-wet with water into which a drop or two of dish detergent has been mixed. Rinse out the mold with the detergent water, then pour in the plaster soup to the brim, and prop up the mold so that the brim plane is closest to level.
Hydrocal is useful poured in tablespoon increments directly over prelaid plaster or other structures if you wish to cover gaps, create rock walls, or build up “earth” at the feet of trestle bents and other objects because it sets up quite quickly. It costs considerably more when you cannot purchase it in bulk…in other words, a hobby shop or a craft shop will charge you more per unit weight/volume.
I have had excellent results with Joe Fugate’s goop ( one part portland cement to three parts DAP wall-patch plaster of Paris, and four parts of fine-ground vermiculite. I had better results with Polly Filla because it took much longer to set up…I could return to tidy up or re-shape after a few minutes, but it costs too much, so I switched to the DAP.
You have received good advice about the cleaning. Do it thoroughly after every single batch that you mix. Having even small quantities of the setting-up stuff from the previous batch mixed with the new will compromise the newer batch in jig time.
Oh, and a big tip. Two, really. Layers should be thin, about 4-6 mm tops. When you add a second for strength or for shaping, spray the first layer liberally with water so that the drier plaster doesn’t act like a sponge and soak up the water from the new layer. If you let this happen, the new layer will have insufficient
Back in the olden days on my first layout, I used Hydrocal-soaked industrial strength paper towels to do hardshell scenery. My understanding, from what I’ve read and heard, is that Hydrocal plaster (A US Gypsum product) is very hard and dense and makes excellent castings with fine details such as tunnel portals, brick or stone retaining walls etc., but it does not take paint washes used to color rock castings very well because of its density. I think most people now use either molding plaster or plaster of Paris for rock castings for this reason. These plasters are more porous and take the paint washes better.
Out of curiosity, I did an internet search under Hydrocal plaster and turned up a couple good references as follows: www.plastermaster.com/usg/ and www.gypsumsolutions.com/htmlID/hydrocal.asp and a website describing the hardshell scenery technique whose web address I can’t get to work, but it’s on the first page of the search results and works from there.
I believe that what people refer to as Hydrocal plaster is in fact Hydrocal White Gypsum Cement.
You should be able to get the name of a local supplier of both Hydrocal and molding plaster off the US Gypsum web site. If you need a large quantity of these plasters, I believe you can buy them in 50 or 100 pound bags for far less than you’ll pay in your local hobby shop.
What do you guys think of Sculptamold? I’ve use it to cover some foam joints (over self-adhesive fiberglass type joint tape). It seems easy to work with and my layout models mostly flat lands with some rolling hills so I won’t need large quantities of it. I plan to do some caving of my 2" foam base and add some hills with additional foam layers. I’ll touch this up with Sculptamold (or some other type of plaster) as needed.
I really don’t know much about plaster. All I know about Hydrocal is it is much lighter than traditional plasters when finished. Plaster of Paris is very cheap and easily available at any hardware store. I did try some Plaster of Paris in rock molds and was not as happy with it as I was Hydrocal. The Hydrocal mixes easier and sets harder (for me anyway).
For my layout I used a combination of plaster soaked paper towels and plaster cloth. I wanted to try the paper towels/plaster because it so much cheaper. After seeing the results, the amount of work, the clean up etc I will use exclusively plaster cloth from now on! I love the stuff.
Consider this comment to be a plaster substitute for certain targeted projects such as roads.
There is another substance that mixes like plaster in the U.S.A. called water putty which is a light tan powder that mixes with water and dries rock hard, and is available in a hardware store for under $5.00.
Water putty is ideal for roads that will be painted some specific color whereas plaster will take readily stains and is much softer than water putty after it dries.
I use hydrocal. What I do is add dry color (black, brown, etc) in with the hydrocal before adding water. Use only a LITTLE color. Mix well and adjust color acording to how light or dark you want it to be before adding water. It works well. Water based washes add the highlights to the hydrocal. The dry colors can be obtained at places like Michaels or other craft based chains.
I like hydrocal, but jeesh it is a bit expensive. I usually use plaster cloth for the base and hydrocal x1 or 2 layers over that if it is on the front of the layout… less if it is in the back. I cast all of my rocks in hydrocal. That being said, I recently had a great result using Durham’s water putty… I use it to cast cement blocks/foundations, because the texture seems to be better for that to me. It also allows you to drill/carve well, leaving nice sharp edges (e.g. for bridge foundations, where you need tight tolerances) Recently, I used it to cast a few rock formations recently and they turned out great. A bit heavier than hydrocal, but MUCH stronger. Oh, as for sculptamold… yes, I use it, usually in between my rock formations/castings or for building stuff up.
As for painting, well, I think it depends on your method. If you use watercolors, hydrocal soaks up A LOT. But I use an acrylic black base follwed by 2-4 washes of colors, 2 or 3 collor blots followed one last black wash and then drybrusing. It may seem like a lot work, but they seem to turn out to me. This technique works on all surfaces, blending them together…
Art plaster or dental plaster is the best for molds. Very strong and takes detail well. Plaster of paris works OK too but not as strong and sets up a bit faster.
For ground scenery from river beds to mountains, I find “structolite” (AKA “gypsolite”) to be excellent; far lighter than POP, nice texture - it looks like slightly rocky dirt or stones depending on how you sculpt it, cheap by the 50 pound bag, you can dye it, takes paint, reasonable working time (20 minutes ±). Full dry time is approx overnight.
What I plan to do is to make several castings with each type plaster I want to test.
First I will find out how I like each type of material to work with, then I plan to try different methods of coloring (that’s why I made several with each type plaster) to see which I like best. May find that some methods of coloring work better on one type of plaster than on others.
Those that I like can be used on the layout, the others broken up for talas or tossed in the trash.
I hope I find it a good way to pre-test the various materials and methods that have passed through my head.
Hydrocal (The USG brand name for white Gypsum cement) is intended for casting applications (like lamps & statues) as it is light weight and very strong. Plaster of Paris is a much denser gypsum plaster product that takes longer to cure and is heavier. It doesn’t hold detail the way Hydrocal does and you might not get the best results using it in rock molds and the like. Structolite (another USG product) is also a type of Gypsum cement that has perlite (little styrofoam balls) added to it. This makes for a light weight and non-smooth base when it cures. It is meant for either a base, or scratch, coat that gets the final coat of finish plaster applied (for walls) or as a setting material for installing fixtures like fiberglass bathtubs on plywood subfloors. It works nicely over a wire screen base layer to give texture to the scene. NOTE: Don’t try to “tint” plaster, or any dry gypsum product, with pigments or paint added to the water as this often results in a gloppy mess as the plaster won’t cure properly. Just use clean, cool water. This is my “let others learn from my mistake” lesson…
I LOVE Sculptamold! I use it for my top layer (over plaser gauze) and “tint” it with my base earth color latex paint so any chips won’t look like white scars. It sets up fine even when I tint the water with diluted latex paint. It has a fairly long working time and can be mixed to varying degrees of stiffness (just use more or less water) so you can apply it with your hands or even a stiff paint brush. I love my local hobby shop but as I only