# For those of us that have plaster paris questions



## BNSF Fan (Feb 27, 2010)

Did a Goolgle search on Plaster Paris. Good article here, kinda lengthy, but informative about using and mixing. Main thing is, do not stir, the more you stir the faster it sets. I did not know this. Now I gotta get a flour sifter.

http://users.lmi.net/~drewid/plaster_faq.html


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## stationmaster (Dec 7, 2008)

I do not use Plaster of Paris. Try using Hydro-Cal. I think you will find it easier to work with and it does not dry as quickly, allowing you a bit more time to work with it. It is lighter than Plaster of Paris and less expensive too.

I found that Plaster of Paris does not accept stains as well either, as it dries too hard. Does well with paint though.

Just me $.02.

Bob


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## tjcruiser (Jan 10, 2010)

Anyone ever fiddle with the powder-mix wall plaster stuff that you'd use on drywall (via Home Depot and the like)? I know that usually comes in a fast set and a slow set version. I've been thinking that this might work for model RR hills and the like, but I haven't gotten around to trying it.

Pros? Cons? Better or worse than plaster of Paris?

TJ


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## stationmaster (Dec 7, 2008)

tj, my opinion? Plaster of Paris SUCKS!!!!! 

Drywall plaster, or mud, the stuff you are talking about, does not lend itself to modeling all that well. An example would be that having the depth of coverage needed in some cases(molding mountains and such), the drywall mud cracks. If you are wanting fissures, this would be the stuff to use. Most modelers do not and want to apply plaster in a " once and done" mentality. And it is heavy!!! Hydro-cal is also used in the building trade, but is a much better product for our use than many of the other products out there. 

I've seen friends destroy modules after using drywall mud. They applied it too thick trying to accomplish the "once and done" thing. Scenes began cracking while drying and out came the hammer. I've had more than one laugh at their expense.

Bob


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## tjcruiser (Jan 10, 2010)

Bob,

Thanks for the experienced advice. I have none in this department!

To be clear, though, I'm talking about the dry powder stuff that one has to mix with water ... NOT the pre-mixed joint compound. (I'm not sure if one or the other, or both, are commonly called "mud".)

Do your comments above pertain to the dry powder stuff?

Thanks for setting me straight here. Again, I've never gone down this road with hill sculpting. To date, I was working strictly with carved foam. But at some point I may venture "off the cliff" (ha ha!), and you're guidance will certainly be appreciated.

Does one buy HydroCal at home centers? Hobby outfits?

Thanks!

TJ


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## BNSF Fan (Feb 27, 2010)

stationmaster said:


> I do not use Plaster of Paris. Try using Hydro-Cal. I think you will find it easier to work with and it does not dry as quickly, allowing you a bit more time to work with it. It is lighter than Plaster of Paris and less expensive too.
> 
> I found that Plaster of Paris does not accept stains as well either, as it dries too hard. Does well with paint though.
> 
> ...


I've never tried Hydro-Cal, so maybe I should, just to see what it's like and compare. Never really had a problem with the plaster paris coloring or otherwise. Can you get the same Hydro-cal at a home improvement store as the hobby shops sell? Seems when I looked at it in the LHS it was kinda expensive. Thanks.


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## stationmaster (Dec 7, 2008)

Available at most home improvement stores. Another product to try is Sculpt-a-mold, I use it on occasion when I'm on a roll and out of Hydro-Cal. I get the Scuplt-a-mold at Hobby Lobby or the local train store.

You can buy Hydro-Cal mixed or as a powder. I have to add water to it if I buy it mixed(more expensive). Powdered is my choice of poison. A 10# box doesn't go as far as you think though. At least that's my estimation.

I think that the way in which you use plaster cloth as a base, its rigidity and such, is key to a good "hill". I probably use too much of it when building mountains, but damn, they sure turn out nice. The Hydro-Cal and Sculpt-a-mold just add so much to the finished product. Add a couple of castings from the Woodland Scenics molds and you have a "hill to remember".(I use Hydro-Cal for the castings too)

Bob


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## Southern (Nov 17, 2008)

I agree with Bob. I use hydro-cal. it works great.


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## Reckers (Oct 11, 2009)

Would one of you experienced hill-sculptors be willing do do a thread on it? It would be useful to hear a step-by-step process, even without pics. I've heard a lot of random descriptions of various stages, but haven't seen a cohesive, start-to-finish description with discussion on here. I realize I could probably go to youtube or something, but don't know the person doing the video. That means I can't ask questions, or find out it crumbled three weeks after he shot the vid. Any volunteers?


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## stationmaster (Dec 7, 2008)

Reckers, there are basically two ways of "building" hills. One, the method I DO NOT use is sculpting foam. 

The second, the method I use, is the "lattice and plaster cloth". I'll try to put together a bit for you. 

A third, used mostly for "bumps" is using wadded up newspaper and cardboard lattice. Not real familiar with it, but have done it other than helping a friend with his layout.

Bob


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## tjcruiser (Jan 10, 2010)

Reck,

I went the "sculpted foam" route for the little tunnel/hill on my HO layout ... for no specific reason, other than I had to try some method. I guess, also, because I have in inclined/curved tunnel within the foam, I needed to control height clearances, and the foam sheet "sandwich layup" gave me that ability.

I glued each layer of foam together with: (a) hot glue, for quick bond, and (b) a caulk-like adhesive specially made for insulation foam sheets.

After rough cut and glued layers, I "went at it" with a keyhole saw (like those for cutting outlet holes in drywall), an 80-grit belt sander, and an 80-grit drum sander spinning in a drill chuck. All a bit messy ... pink stuff flying everywhere! I was going for a rough, ragged, natural look, so the process worked sort of OK. The contours of the hill look fine, I think, but the bottom, near-vertical edges don't really have a smooth transition into the abutting/surrounding terrain. Not very lifelike there.

The foam painted quite nicely with latex or acrylic paint. I "dry-dabbed" on 4 or 5 different earth-tone colors, with each showing through for a rocky look.

If doing this again, I might try the "crumpled newspaper covered with plaster cloth" method, if only to try something new. I've seen a few guys here on the forum (Anton, I think?) make their hills from crumpled aluminum foil. The facets of the foil really gave a nice, realistic "chiseled" look to the rock face.

Pros and cons to any method, I suspect ...

TJ


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