I’m building an 11x15 two level HO layout that replaces a previous one built (1993-2008). As this is probably my last layout of size (I’m 66), I have tried some new and different (to me) stuff in the construction. In example, I used latex caulk for roadbed adhesive (always used brads before), took the jump into DCC, etc., etc.
I’m currently putting in the perimeter scenery that will blend the layout edge into the backdrop. I’ve glued down scraps of wood, stapled in some nylon screening, and did a first coat cover of paper towel strips soaked in plaster. On previous layouts, I would have added a second/third layer of plaster, and work it into rockwork or groundcover base.
However, I picked up a tub of joint compound and thought I would use this instead. While I have used JC for its intended purpose (floated drywall joints), I have never used it for scenery base.
Sooooo, what hints and tricks do you all know about that could help me do a better job?
Thank you!
Mobilman44 - living proof that an old dog can learn new tricks! _
I use joint compound all the time on my N scale layout. The only place I’ve used plaster is for rock castings. I’ve never had a problem with it flowing or sagging on vertical surfaces. Keep the coats thin. You can always add more coats. Thick coats will crack. When I use it for roads, after it has almost set up, I smooth the surface with a (not too) wet sponge to get it perfectly smooth. Even after it has set up, a wet sponge will still soften and smooth the surface. It’s fairly easy to do some carving in it after it has partly set up. For working the compound, I use an offset trowel. You can get one in the kitchen gadget area of your supermarket as a cake decorating tool for applying icing or in a craft store as an artist’s palette knife (probably more expensive). Using the premixed kind in a tub is much more civilized than using the powder and mixing it with water. The lid on the tub I’ve got now fits so tightly it’s a fight to get it off each time so I’ve had no problems with the contents drying out, but if the lid doesn’t form an airtight seal, cover the top of the contents with a little water and pour it off when you go to use the compound. I have found that I can dilute the premixed compound with water to make as soupy a mixture as I want. The leftover will keep for a very long time in an airtight container. It takes paint and stain about the same as plaster. There are different types of compounds with different characteristics such as hardness and setting times but I just grab a bucket off the shelf without paying attention to that. I can see where it would matter to a drywall hanger, and a quick setting compound may not give us enough time to work it and carve it. I understand that it doesn’t produce as hard or as smooth a surface as Hydrocal does. I’ve never dampened the surface I’m applying joint compound too, even if it’s going over plaster cloth. It doesn’t seem to suck moisture up like plaster does, but I’m open to being proven wrong on that point. I’ve just never had to do it.
I’ve never had good luck with joint compound on scenary. Big tendancy to crack when applied thick enough to shape. The only success I’ve had is when using it on a solid substrate like foam board as a very thin layer to smooth out the foam and provide a paintable surface. Basically when used just like you would on a wall. Otherwise plaster does a much better job.
I used it on a test module, that I since dismantled due to other reasons, but I think it was Joe Fugate who used vermicilite or something over masking tape. I found that the masking tape served as a good “base” for the use of joint compound. I never put it on in over 1/4" thickness and I never had an issues with sagging or flowing. Granted, I also didn’t thin it with water either. I’ll probably use it again as it was not messy at all.
I used it on my Nscale layout for all the scenery. I cut up 2" x 10" strips of brown paper bags from the food store. I took the joint compound , pre mixed kind from the local home store, and mixed more water with it so i could dip the paper strips in it. Then i applied this over newspaper forms ( like using Hydrocal) . It worked great , is very strong and cheap and ez.
I used joint compound on my present layout and found it to be satisfactory. Keep the coats thin. Allow adequate drying time between coats. For making rock shapes with it I would coat the mold with a thin layer of Vaseline then put in a thin layer of the compound and allow it to dry. This gave me a casting that was hollow and light but still stiff enough that it wouldn’t crack.
I use joint compound all the time, though not by itself. I make up a mix of papier-mache and joint compound, in roughly equal amounts, to which I also add color and texture agents. I apply this over my foam base, which is expanding foam that I have carved to rough shape. The fibrous cellulose of the papier-mache (I use Cell-U-Clay brand) makes the plaster hold together in clumps, making it very workable and clean in comparison with old fashioned plaster, which wants to slop over everything and requires careful masking of critical features like completed track or structures. With my mix, I never mask anything! I just blend components one plastic cupful at a time, and trowel it on using a plastic spoon (or a metal one if you requisition one; all components are water washable so you can theoretically clean it off later).
As others have indicated, when applied thick, it will shrink and crack. This is even moreso the case with my mixture, as the Cell-U-Clay shrinks when drying. However, it remains workable when wet again, so all I do is let it dry out thoroughly and let the cracks happen, then re-wet those areas and work it a bit more, perhaps adding plaster but usually just smoothing over the crack.
Of course, I’m not relying on my “Soil Layer” for structural strength; the foam below (or whatever base is used) supports it. I developed my technique when I was an apartment-dweller, looking for a scenic method that was not sloppy, which imparted the right color and texture of soil throughout the plaster rather than being painted onto a white surface, and which would be ideal for portability. This last criteria means that I wanted something of lighter weight, that was not as brittle as hydrocal, so that minor stresses of movement would not later produce fractures. My N-Trak module has been going to shows for five years now with no signs of wear-and-tear in the scenery, because this method is relatively “soft”. And planting trees is great; just wet it with a drop or two to soften, poke a h
I have used both the ‘pre-mix’ buckets and the bagged stuff you have to mix.
Pre-Mix buckets - easy to use, but when it dries it is ‘rock hard’ and does not sand very well.
Bagged - I get the ‘Sheetrock’ brand in 18# bags. you can get anywhere from 20 minute to 90 minute setting time. I like to use the 45 minute bags. It is easy to mix, and I can thin it down enough so I can ‘paint’ it on with a old stiff bristle brush. It sands very well and fills good. Most of my scenery is medical plaster wrap with drywall mud painted over it. The rocks are Plaster of Paris castings(take stain much better than Hydrocal). I sometimes paint Hydrocal over the plaster wrap to stiffen large areas.
I can’t argue with your personal experience, but I am amazed that 1) you find “rock hard” to be a problem-it is supposed to be-and 2) that it doesn’t sand well. I have yet to use joint compound on a layout but have applied countless pre-mixed gallons of it (usually USG Sheetrock brand) over drywall and plaster surfaces. It sands very well in my experience and can also be smoothed with a damp sponge that softens the surface enough to produce the smoothness when the sponge is used with a light touch.
Also, the adhesive-backed mesh tape is a terrific base for the product compared to the age-old paper tape.
The ‘pre-mix’ stuff I have is Sheetrock brand "lightweight all purpose joint compound’ with a ‘plus 3’ logo on it. It does say ‘easier to sand’, but it really dries quite hard. Sanding it smooth to remove the the ‘marks’ from spreading is quite hard. The bagged stuff from the same manufacturer is a lot cheaper, mixes easy and has a 90 minute setup time. It also sands better. I just have more ‘control’ over the stuff. The small 1 gallon pre-mix bucket is used for home repairs. The other half is always redecorating…
the adhesive backed ‘tape’ is great stuff - it has even made it to the layout where large modules are added - fast way to seal a seam before adding the ‘mud’ and ground cover.
Thank you all for your help - as always it is very much appreciated.
I’ve been working with a pre-mix tub the (started last evening) of some LaFarge pre-mix ($7 @ Lowes) and have used it in two different types of applications - all with apparent success.
I had a 3ft long, 3-5 inch high curved “wall” that has nylon screening covering the opening. Yesterday afternoon I spread some pre-mix over it (thin coat), in order to stiffen the screening and provide a solid base for a second coat, followed by plaster rockwork. Well, this morning I found it had stiffened nicely, and then I applied a more thorough second coat, smoothing it horizontally with a wet 2 inch brush. It looks good, and should be a perfect base for a plaster coat and rockwork strata.
I had applied a layer of plaster soaked paper towels over some small pieces of wood along the edge of the layout, to ultimately give it a small rise that would flow into the backdrop. Normally, I would usually apply a second layer of paper towels, followed by brushed in plaster. Instead, I lay down some “globs” of premix and then smoothed it out over the towel layer with a wet brush. The towel seams just “went away”, and I think it will make a great base for the final plaster coat.
I’m really glad I gave this a try, as it is less messy (than plaster) and does the job. Of course it is not an “end all” to scenery work, but is just one more tool/method that we can use to get the job done.
