Yes!

We're using the regular weight 15 kg premixed boxes of mud, and kitchen paper towels, over cardboard strips. Working beautifully.  One warning - our box was left open for two days, and though still usable we had a green fungus growing, so we discarded the remains of that box. We usually open the box, extract a margarine tub of mud, and close up the bag liner immediately, expressing all air.  To the removed mud we add a concrete tinting agent, and water to get the consistency required.  Wear gloves, as drywall mud is hard on your hands.

Blair

Plaster of Paris

Never looked into the chemical compostion...where it falls between Hydrocal or wall mud...but have been using it for years for scenery and road crossings. Very easy to work with.  And for road crossings...if you make the right tool to clear flange ways...no problems what so ever.  During this next build of mine Im going to tint the plaster...add paint to make sure...when I clean the track..no white plaster shows up after scrubbing/rubbing.

Craig Vreeland of Sterling Models

Introduced me to the idea a while ago.  I just bought a bag and am going to try it this or next month.  I’ll keep you posted and also be following!  Quite fortuitous!!!  Craig’s website has a method for mixing it with perlite too. http://sterlingmodels.com/wp-content/uploads/Lightweight-Sculpting-Compound.pdf

Nick

pre mixed sheet rock mud

works better for thin coats.  Water mixed mud or a putty product like Fixall or Durhams is better for filling larger gaps and laying down thicker layers. Plaster is a different material than sheet rock mud and has some strength and durability advantages. That said I'm using Fixall and sheet  rock mud on my new layout as it will be adequate for the simple scenery I'm building. I'd suggest reading up on the difference in the materials then making a choice based on which you think would be best suited to your layout...DaveB

Lightweight Spackling

I work on foam, mostly these days. I use the Dap "Patch-n-Paint" to smooth out landforms, fill holes, make crossings, build small hillocks, and take care of sharp edges. It's VERY close, if not identical, to what Woodland Scenics sells as "Foam Putty". Put it on with a putty knife or palette knife, thin with water if necessary, sands easily, dries fast, paints over well. 

And it's light.   VERY light.

One good use is to seal the foam before pouring gloss medium to create water features. cover the bottom and banks of the area, sand smooth, paint your bottom, and pour the gloss medium.

If you DON'T seal the bottom with more then just paint, the foam will gas out through the medium in a week or two and it'll be full of champagne bubbles. You'll have to tear it out and start over.

Don't ask!

Drywall Mud

My experience. I have used it for scenery work. I have used thinned paints and pigments as stains to color the rockwork.  It will not take stain like plaster, It can be painted just fine. If applied too thick; it takes forever to dry and tends to crack as it shrinks. This can be good or bad depending on what you are wanting. I have never tried casting with it , but doubt that it would show the detail as well as plaster.

Espee over Donner

Other Plasters

Hydrocal simply isn't necessary.  Other brand names, including from US Gypsum (the manufacturer of Hydrocal) work just as well or better for building scenery, and some are far cheaper.  See USG's sites at  https://plaster.com/ and https://www.usg.com/content/usgcom/en.html for more, including ordering or finding a supplier.  I use USG casting plaster for nearly everything.

pre mixed sheet rock mud

I saved all the fiber (Pulp) shipping protectors I could find and when it came time for scenery, they came in handy

I also salvaged a food processor (don't swipe the wife's)  and used that to grind up the pressed pulp with water.

Mixed that with premixed joint compound, applied it to the layout and never looked back. No problem with cracking or spoiling after 5 years in use

Jim.

I used to be able

to get casting plaster at the local lumber yard but not anymore. It really depends on what you are trying to accomplish. I use drywall mud but only on top of drywall tape for seams in the backdrop. I've used it in the past for forming small mountain road surfaces and it worked just OK. I would go for plaster (casting, Paris, ultracal or hydrocal ) for anything I wanted to be strong and/or thick.

My fears have subsided

Thanks all for your input. I have two boxes of Hydrocal and will use them for molds, but probably get a bucket of the lightweight mud from the hardware store and proceed. I was afraid of cracking and other issues. But it seems that is not a problem if properly applied. 

Thanks!

Mark

I used the premixed mug in a bag ONE time.

After the dried pieces on it inside flaked off into the good stuff I switched over to the bucket of mud.  Just be sure and wipe all the unused mud off the inside EVERY time before you put the lid on.  Laying a damp paper towel in there also helps.  Adding some earth color now sure seems like a good idea.  If you put it on too thick it will take longer to dry and cracks will develop that are easily filled with the following coat.  Don't worry about the cracks, it just because of shrinkage.

Tehachapi mud

Drywall mud was used for lot of the scenery on Tehachapi.  Works just fine.  Maybe the only concern is that it remains water soluble under the paint.  If the fire sprinklers ever went off, a lot of the layout would wash away.

Come to think of it, that probably would be accurate prototype modeling here in Southern California.  < g>

Taping mud

I usually buy a one gallon bucket of standard taping mud at the local Home Improvement store. I've gone through 3 buckets so far. I'm covering cardboard strips with plaster cloth and then covering that with taping mud put on about 1/8" thick with a 1" wide putty knife. Before it dries I go over it with a 2" wet paint brush to smooth it out some. If cracks develop I just spread a little more over the crack before painting. You can see my results at http://www.pbase.com/campgus I had to remove a small creek where the resin never cured, it was pretty easy using a Dremel to cut through the substrata.

Gus

Pre-mixed Drywall compounds

Mark,

I have been using it for 9 years on my layout without a problem.  The only time I had issues with cracking is when I put it on too thick.  When that happens I just fill the crack or make it part of the scenery. 

Andy H

Too much dust

I have banished the use of plaster for my hard shell.

This produce too much dust specially when you do scenery on an existing layout which is already sceniked in part.

I use Red Rosin Paper hard shell, strong as plaster shell, no dust any more; rock molds are glued dry on the surface.

And for the price a roll of Red Rosin Paper is enough to cover acres of mountains.

I also use a "goop" paste to form some ground forms  for my scenery, again no more dust with this stuff and no mess too.

I used lightweight mud to cover a joint in the backdrop.

It was soft and easily dented. I couldn’t sand it at all and had to cover it. For general scenery it’s probably great but for something that needs to be hard and sanded it sucks. It drys to the consistency of foam rather than sheet rock. 

DuroBond, and StructoLite

All of my castings were done with DuroBond (you can get either 45 or 90 min set); very cheap and great to work with in molds.

The rest of the scenic shell is drywall shims (cardboard strips, but pre-cut - used for window installs), and plaster cloth bandages from eBay or other sources.  Then, a layer of StructoLite over that - again, very cheap, lightweight, but really strong.  It's a rough texture, and in my case I like that as a base.

Cracks

Typical drywall mud will crack if put on too thickly.  I personally prefer plaster of Paris, bought at Home Depot (paint  dept) in 25-pound bags, for most other work, like rock castings, etc.  The bags of PoP are cheap ($10 or so IIRC).  To keep drywall mud from growing or drying out, when finished for the day I smooth the surface of the mud in the bucket and place a piece of kitchen plastic wrap directly on the mud and against the walls of the bucket, smoothing it so there’s little or no air in contact with the mud.

Great for roads

I use drywall spackel and mud for roads. Works great and takes paint and washes well.

My roads

are also spackle or drywall mud. And yes, heavy coats crack, multiple thinner coats are less likely to...

Drywall Shims

@Steven-  What a great idea.  I once helped a friend cut up dozens of cardboard boxes to support his scenery what a mess. Even using a bandsaw it took about an hour to cut the amount needed and the different lengths made it a pain to cut and install.  I wish we had known a 3 1/2 foot long 100 strip bundle could be bought for $10 at the local big box store; saving a lot ot time and frustration,

Thanks for the suggestion.

Lou in California.

@Joe Circus,

That's in line with our experience so far; we're using cardboard for terrain shape, and adding paper towel soaked in diluted, tinted joint compound; no cracking, because the technique doesn't lend itself to thick application.  Rather, we're applying multiple layers to build up thickness, and each layer dries before the next is applied. 

Blair

@Amsnick

Nick (and all),

I tried Craig Vreeland's method after reading the PDF you provided the link for.  But...  I couldn't find any Perlite locally, that was just plain, with no additives, so I ordered a bag via Amazon.  Problem is, the bag arrived labeled as "coarse".  Oops!  That would leave my mixture way too lumpy, I thought.  So I put some in a Ziploc bag and hammered away on it with a rubber mallet, trying to reduce it to a finer particulate.

Didn't work very well...  still had clumps, and some of the crushed stuff still clung together when I mixed it per Craig's recipe.  Live and learn - "fine" grade Perlite is needed.

But…  I went and dug out a partial bag of fine Vermiculite and tried making Craig's mixture with this, vs Perlite.  Notice I said "fine".  Worked very well!  I got a nice mixture that wasn't "ice cream smooth" as Joe F. put it.  Had a nice texture to it.

I added a bit of brown concrete color to the mix, to tint it (a little goes a long way!).  And after applying it to my scenery (just filling in some too flat areas between roads and track and such), I sprinkled on some builders sand, just to give it a variety of color/texture.

The next day, maybe 12-15 hours after I applied it the previous evening, I found it was still a bit soft, soft enough that I could easily scrape some high spots and so forth.  Now, 3 days later, it is hard, like drywall mud should be, but no shrinking or cracking.

I should mention that I used the "90" mixture (90 minutes working time), and I bought the bag at Home Depot.

I like this process, vs the more common "ground goop" recipe.  Less ingredients and easy to mix.  I did add just a bit more water while mixing the stuff up, so it spread easier.

Al Carter, Mount Vernon, WA

There is a difference between mud and plaster

Drywall mud may be easy to work with but it is soft and easily damaged. It will dent and scratch easily. It will soften back into mud when it gets wet. If applied thicker than about 1/4 inch, or in dry weather, it will shrink and crack as it dries.

Plaster or hydrocal or ultracal are used for casting hard, durable, and detailed items. It cures through a chemical reaction to harden rather than dries.

Use the plaster products for fine, permanent features. You can use mud for temporary ones where surface detail doesn't matter, or for patching holes or cracks where strength is not an issue. A 50 pound bag of hydrocal can be had for not much money.

Lightweight hydrocal is a proprietary blend of ingredients by Woodland Scenics. It's basically hydrocal with a light filler material. It's a little more difficult to mix than regular hydrocal but it holds detail like plaster and it's significantly lighter than plaster when cured. Unfortunately it's a bit expensive and I've never seen it in bulk.

In between these extremes is water putty. It dries hard and brittle, can be tooled when wet, and can hold decent detail. It will turn back into putty when wet. I've seen it used to great effect to make realistic rutted dirt roads. It will take stain or paint as long as it isn't wetted and worked too much. Some folks really like it and it isn't expensive.

These are only a few materials used to build terrain. Different products, different uses. So for this question of mud versus plaster, I would say it's really a question of soft and easily removed versus hard and detailed.