A section of my layout I am modeling a sheer rock wall, approx. 14" high, by 40" long. These are rocks I made with the WS rubber molds. What is the best way of attaching these to the foam board, in the past I have used joint compound, hot melt glue for attaching the rocks, but that was always to a hillside that was on a slope. This wall will be almost verticle. Last thing I want is for them to come crashing down 6 months form now. I can put a slight incline in to wall if that will make it easier to install the rocks if needed. Thank you for any advice you can give me.
I would recommend PL300. It is an industrial constructon adhesive and works very well. However, do support the castings for about 24 hours until the caulking that PL300 is hardens somewhat. It takes a while in my experience. Failing that, any cheap acrylic latex caulk.
Regardless of what you eventually decide to use, do score up the back of the casting and also the foam. You want as much surface area as possible for the adhesive to grab onto in order to do its job.
Crandell
Selector gives some good advice. It is important to use a good adhesive as he has recommended and support the rock castings until it is cured well. I would not try to place all the rock castings in one go. Place the lower ones first and after they have cured move up. I would also recommend that you add as much incline to the wall as you can. In the real world rock walls are cut with as much slant as practical to add some stability.
Joe
Connecticut Valley Railroad A Branch of the New York, New Haven, and Hartford
"If you think you can do a thing or think you can't do a thing, you're right." -- Henry Ford
I'll go along with latex caulk and scoring them a some.
To fill in between castings, many folks use Sculptamold. I have used it to secure castings, but one as tall as you are doing, caulk with Sculptamold between.. You can fill in between after they are in place or you could put some around the edges so it pushes out a little between the castings. Be sure to shape it before it sets up.
Good luck,
Richard
I just finished a large rock canyon and agree that using sculptamold beween the rock faces is a good idea. However once you get the larger rock faces applied use the smaller ones to fill in the gaps hold in place and sculptamold around them that will make them stick. Start from the bottom and work your way up. Once everthing is dry use a sharp utility knife to cut into the plaster and sculptamold you can use alot of the same rock castings this way and then change them up to look atleast a little different. to critique it just the way you want it. The object is to have more plaster rock formations than sculptamold, good luck happy carving.
Hydrocal itself will bond to the extruded foam. If you have uneven and/ or shaped portions of the foam base, you can apply the semi-dried mold directly to the base. i will always "butter" up the back w/ some fresh mixed Hydrocal then press, shape and will allow to conform to the base. You will feel the plaster/ mold get warm. I will hold the mold in place until it remains, this may take a few minutes. Don't peel the mold off until the casting sets- at least 5-10 minutes. I don't worry about the ooze out, this can be removed or left to carve as you fit additional castings either whole or broken. A good hint to any casting that you want to shape or break is to not fill the entire mold to level. Rock the mold and allow the plaster to cover just enough that it is 1/8 to 1/4". These will break apart quite easily and by placing w/ buttered Hydrocal many pieces can be placed in a relatively short time. I will examine the castings and get a feel for the shape, strata, and position of the larger ones. When doing such a large cut, you just need to not have that "patchwork look. You can use the same mold over and over. but change it's orientation and use care that any obvious shape/ feature of the mold won't look to repeat itself. Other chunks/ bits that need to be added can also be placed w/ Sculptamold the excess of Sculptamold is far easier to carve, shape or remove over that of any forgotten blobs of hardened Hydrocal. A hint to carving the curded Hydrocal is to wet it down, you'd be surprised as to how easily that "rock" hard plaster will cut.
These areas done w/ this method
Now this spot really wouldn't work w/ all the castings and carving- it was just too massive and the shale would not have come out right. i used the cripplebush "rubber rock"
The rubber rock may seem a bit pricey for most, however, even w/ my experience, I wouln't have been able to replicate this shale to this extent by the individual placed and carved castings. This cut is 14-16" height and over 10 ft long.
Modeling B&O- Chessie Bob K. www.ssmrc.org