Woodland Rock Mold

[pls12]

I will begin placing rocks (rock mold) on my mountain side

Instructions say Lightweight Hydrocal but it sets in 3 min. I want to place them on my mountain which is a curve so I need them not to set up so fast I want to follow the curve,they will need to be a little flexable. What else can I use that won't set up so fast?

[twhite]

I've had fairly good luck with Sculptamold, a papier-mache/plaster mix that I think has been discussed on this forum in the past.  The package instructions have hints for using the product in molds (increasing the water content) and the material stays flexible much longer than Hydrocal.  One drawback--if indeed it IS one--is that the texture, after the Sculptamold dries, is 'grittier' than Hydrocal, so your rocks will be a lot 'rougher' looking than Hydrocal.  However, it does work quite well in the WS rock molds, but has a much longer setting time.  But that also allows you time to do more detailed carving if you wish. 

I like it.  Most of the existing rock-castings on my Yuba River Sub are Sculptamold. 

Tom

[bogp40]

I will begin placing rocks (rock mold) on my mountain side

Instructions say Lightweight Hydrocal but it sets in 3 min. I want to place them on my mountain which is a curve so I need them not to set up so fast I want to follow the curve,they will need to be a little flexable. What else can I use that won't set up so fast?

The 3 min. setting time is more than enough to place the mold. When you mix the Hydrocal make it a bit soupy and use cold water. Generally when filling molds, I'll have pieces of rolled paper towel to prop the mold to keep it level. Have a few extra molds on hand so that after your initial pour any excess can be placed in them for future use and not to waste.

After a couple of min the wet/gloss starts to soften and the plaster will start to thicken. As soon as the mold can be handled w/o slopping the plaster, place it on the desired location. Many times, I will mix a small second batch to use as a butter to place the casting (a too dry casting, even though pliable, may not be wet enough to bond).

Hold the mold in position using presure to conform to the contours. You will feel the mold getting warm. Once the mold will stay in position you can ease off on pressure or holding  altogether. Usually after a few more minutes the casting will harden. To check, peel a corner back to see if if releasing properly. Even a stuborn mold can be saved by letting it sit-overnight if nec. After you strip the mold from the casting, cleaning is very important, any small specks of plaster remaining will degrade future use.

To prep a mold before filling, I only wet the mold w/ water and detergent and drain.

One thing I will always do for rock molds is to use dyed plaster. These castings are used on a club layout where handling and some abuse will inevitibly occur. I use powdered masonry dyes. They are added to the dry plaster until a desired color of a gray/ brown is obtained, the this is added to the water, not water to the plaster. Obviously, some experimentation is needed to get the amounts, coloring and your speed of pouring and setting to have the best success. I will usually do this w/ some help so to have the extra hands to hold molds or run for additional supplies or clean stripped molds as the work continues.

I hope this lenthy response can help you create that beautiful rock scenery.

[G Paine]

After a couple of min the wet/gloss starts to soften and the plaster will start to thicken. As soon as the mold can be handled w/o slopping the plaster, place it on the desired location. Many times, I will mix a small second batch to use as a butter to place the casting (a too dry casting, even though pliable, may not be wet enough to bond).

Before setting the mold, it is a good idea to spray the surface where you are going to apply the rock mold with water from a misting bottle. Dry plaster will absorb water from the plaster in the rock mold and will affect its drying.

Also, I prefer the Color Rite molds to the Woodland Scenics; they are more flexible