Hypertufa Slab

Originally Posted by JLB

I am sending this a pm to see if you can understand it before posting.

I have made several slabs using cement, peat moss and vermiculite. I added fiber obtained form the local cement company. The fiber is used to reinforce cement floors, foundation, etc. I use equal parts of cement, peat moss, and vermiculite. For each slab I add cement coloring, purchased at Home Depot. About a cup per slab is enough. The best color I have found is a half-and-half mixture of brown and black. To this I add a handful of the fiber. Mix all the ingredients dry and then add water to make a thick paste. Be careful with the water, it is not hard to get to much water. If you do you can add more of the dry mix.

For each slab you need a piece of plywood larger than the slab and a piece of plastic, I use garbage bags.

Cover the plywood with plastic, dump you mixed dry stuff on the plastic covered board, start adding water until you have a mixture of stiff mud. Work the mixture into the desired shape. Thickness is really a function of size, the larger the slab the thicker it needs to be. For most 2 feet or less a thickness of 1 inch is plenty. You can taper the edges some. When you are all done with shape, size and thickness you can put a rolled towel under the edges to raise the edges to make a slight bowl look and give the slab a more natural look. Put the towel between the plastic and the plywood board. You can raise the slab slightly by pulling the plastic us and pushing the rolled towel under the plastic. Work your way slowly around the edges until you have the desired shape. You can make some nice shapes with the side at different heights. If you have cracks when working on the edges just smooth them out with a wet hand. You can use a stick to make drainage holes now or wait and drill them later. Take the whole thing and put it in a garbage bag and close the end. This allows the whole thing to dry evenly and slowly. After a 3 or 4 days you can carefully take it out of the bag and make sure your drain holes are all ok or drill drain holes using a normal ½ in drill bit. The slab is still quite soft and is easily broken at this stage so don’t move it too much. If it seems hard enough you can take it off the plywood but his is not required and increases the chances of breaking the slab. Put it back in the bag and sit it on a shelf somewhere for about 4 to 6 weeks. This allows it to dry slowly and being sealed in the garbage bag keeps it moist. When it comes out of the bag after curing use a wire brush to give it a more natural look. The whole process is harder to write about than do. The mixture is not written in stone and people use many different ingredients. The one thing I think is essential is the fiber. There are a variety of colors available and the slab can be painted after it is cured. I almost forgot when the slab is done curing you will have some fiber sticking out of the surface. I use a propane torch and go over the slab and all the little ends of fiber disappear.

To make the slab once you have mixture you can use a rolling pin to roll out the slab but I usually just use my hand. Rubber gloves should be used. Cement is hard on the hands. A word of caution with peat moss, don’t breathe the dust, as it can be harmful. I have found that if you are gentle in dumping when measuring and mixing there is not much dust. If this is not clear let me know and I will try to help.

John

Originally Posted by pootsie

JLB sent me a PM with some good info, so with his permission, here it is:
Tanx, JLB

pootsie