I have always used hydrocal for my forming of scenery with paper towels. And I’ve always used hydrocal for rock molds. But what would you recommend for workability and an extended length of working time? A plaster that is durable and still some what as strong as hydrocal. There is virtually no working time with hydrocal.
Thanks,
Chris
There’s no one “best” plaster since we all work differently. I’ve never liked Hydrocal much, and prefer using casting plaster (I can usually work with a batch of 20-minute casting plaster for about 1/2 hour before it totally sets). There are various formulas that yield different setting times, and you can order online from US Gypsum here http://www.plaster.com/ or order through a local store. The site I listed has product descriptions and various hints on plaster use too.
I use Durabond patching plaster, from Canada Gypsum (also available from U.S. Gypsum).
It has a catalyst which causes it to set in a predetermined time, and there are several setting times available. Other advantages are that it can be mixed to various consistencies without affecting the setting time or strength, and can be applied in as thick or thin an application as is required, without noticeable shrinkage or cracking. It can be sanded somewhat before fully cured, but it’s very hard and durable (non-sandable) once cured.
There’s a little more info on it here: HERE
Here’s a semi-finished area, with Durabond 90 (90 minute setting time) applied over aluminum window screen, supported by temporary wood risers. Once cured, and with the risers removed, I can lean on it without worry, a good thing, as this scene is fairly deep.
I apply it to the screen with a drywall knife, then use a cheap 2" brush to smooth out the knife marks before it sets, dipping the brush often and liberally in water.
It can be painted or stained: I started to paint it using full-strength interior latex paint, but found that thinning the paint with an equal amount of water made it much easier to apply while still giving decent coverage, and the paint will, of course, go a lot further. [swg] Once ground cover is applied, it looks fine - the little bit at the left, both between the tracks and below the bridge, was added to take advantage of glue run-off from ballasting and adding the rip-rap to the bridge approach tracks.
I also used it to mak
Awesome layout and pictures Dr… I got tired of Hydrocal,too dry,too watery and too quick to set. Could never get the recipe right. I’m now using DAP pink spackle. it goes on pink and dries white. It applies easy, and easy to sand the rough edges. I still on the learning curve with it as far as thickness when applying,but no complaints yet.
For any kind of plaster mix, I have gotten good results with a 50-50 mix.
Hydrocal plaster was promoted mostly for the first layers of scenery where light weight support was needed because it is strong.
For making castings, Plaster of Paris or casting plaster works better. It is easier to work with after it dries because it is not as hard as Hydrocal and can be chipped away if necessary.
You can make the setting time faster by adding a small amount of salt to the water. To make the plaster set slower for more working time, add some vinegar.
I wanted to try Hydrocal but couldn’t really find a good source for it so I started using Plaster of Paris. For me it works fine for rock molds and that is about the only use of it I have. I will use Sculptamold for blending castings into the scenery or ground goop.
Dear Wayne
That’s some mighty beautiful work you’ve done. Thank you for sharing.
–Jaddie
Thanks for your kind words, Jaddie. There should be lots more layout pictures around, but they’re usually in response to someone else’s thread or post.
Wayne
You could just skip the plaster all together for textured scenery. No chipping cracking and very lightweight when dry. ( 1-2 oz per sq ft)
http://www.flickr.com/photos/wsdimenna/sets/72157618491275941/
I use the ground goop using the formula that Joe Fugate offered us on the forum years ago. I use two parts plaster of Paris to one part Portland Cement and four parts fine vermiculite. I add a pinch of masonry dye powder to get a more earthen tone to the mixture which dries two or three shades lighter than it appears when first placed wet. I first cut strips of aluminum window screen and hot-glue it to supporting elements on the layout’s basic structure and frame, then suppot the screen with plastic shopping bags stuffed with crumpled newspaper jammed in behind it to keep it from saggin under the weight of the wet plaster. Then I mix batches and lay it over the screen.
While it is setting up, you can carve it, and you SHOULD spray glue and sprinkle it with a couple of shades of ground foam before it dries if you intend to cover it. Once it dries, it will be intensely hydroscopic and any glue spray you use will be absorbed long before you can reach for a shaker and dust the surface with ground foam.
It is easily drilled to form holes for utility poles and tree armatures or dowel bases of any size.
Crandell
I use a product called Sculptamold, a mixture of plaster, shredded newspaper, and glue. Very strong, very hard, and your working time is about 30 minutes (although you can extend this simply by using more water). I have a silicone mixing bowl that holds about 2 cups, and I can make several batches right in the same cup without cleaning.
I’ve use plaster cloth for large expanses, but for rock castings, I use casting plaster. If you add a little vinegar to your plaster mix, it extends the working time. And, it takes stains exceptionally well. I let the plaster set up until the plaster cracks, then I spray the area the casting will go with wet water and press the casting onto the layout, making sure to press the edges of mold extra hard for the edges to make good contact. My scenery base is foam, so I made some “pins” out of wire hangers with a point ground into one end, that have been bent to 90° angles. This holds the mold in place while the plaster sets up.
After the plaster has set up, I carefully peel the mold off, then I mix up a thicker mix of plaster (again with vinegar added to extend working time) and use it to fill any gaps between the plaster casting and work it into the gaps with a 1" putty knife. I tried patching plaster, but it doesn’t takes stains as well as the casting plaster.
A plaster product that gives you 2-3 hours of working time is called Plaster Wall Patch (#10304) by DAP. You can get it at Acehardware.com or walmart.com and ship it to the store for free. Good stuff. Sheetrock Easy Sand 90 is another one. Similar to Durabond but 25% lighter. Easy to buy at Lowe’s / HD. Good for 1/8" thicknesses.
I have Hydrocal and started out dipping paper towels in this for the hard shell. Then I gave Woodland Scencs Plaster impregnated gauze a try and haven’t looked back. I also use Sculpt-a-mold to cover the gauze hard shell where I haven’t used rock castings or to fill in the land forms around the rock castings. I now only use the Hydrocal for casting rock faces.
I too much prefer Sculptamold over expanded styrene foam. It has adequate working time, gives a more textured surface and is easily pierced with an awl for planting trees. Sculptamold can be ordered online from Walmart and picked up at your local store which makes it readily available most anywhere.
The best castings I’ve ever done were with Bragdon foam and their molds.
This is a 2-part chemical mix, and there is a lot of preparation. However, the results are really the best I’ve seen.
And, as for adding vinegar, don’t use wine vinegar from your kitchen. It will make your layout smell like salad for a week. You don’t need to ask how I know this.