To make a large trough, you need an inside box, and an outside box. You would have better luck with this "form". Hypertufa tends to slump a lot. I covered a large bowl on the outside, and I fought slump all the way.....so now I use a larger bowl, and a smaller bowl. and put the hypertufa mix in between.

A twelve beer box inside a two-four worked well for me! LOL..got to drink the beer too! Canadians,eh?

You can also use chicken wire or hardware cloth to give the mix something to grab. Set the box on the wire, draw up one side at a time and cut it so the mesh meets at the corners. Then "sew" it with wire at the corners. Smear your mix over that, being sure to work it well into the wire so it goes through the wire and the mix "holds hands".

Sue

You don't have to have the two boxes, you can build just on the outside of a single box. The most important thing is to make sure the box is firm enough because you will need to apply some pressure to mould on the tufa and build up the sides, but with a little give so that you can get it out when you are finished.

If the mix won't stick to itself then it is too dry. Try patting it into place, that encourages water to move out of the mix and stick it all together. No joy, add a touch more water. If the mix slumps then it is too wet.

For a tall trough it may be better to mould between two boxes. Or use the wire mesh. Or build it in two or more sessions. The sides of the box will have absolutely no strength when they are first applied. The corners and the top/bottom will help to hold it all in place.

thanks everyone for your suggests. I am beginning to think my mix was too dry, it was more so not sticking together and staying in place. Also I put plastic on the box, would this have caused it to not stick in place as well as this made the box slipper.
Lynn

You have to use the plastic. Hypertufa sticks very nicely to carboard, but you'll never get it off! It also sucks water out of the mix which will weaken it. I also oil the plastic lightly to make sure it releases easily.