I want to make my own wood float for plastering with lime.
Anyone got any suggestions for a good tool? I understand from reading around that cross-grained is best, but what to finish the surface with? i.e. varnish etc
Cross grained is for rubbing up and closing cracks on plaster; for laying on you use a straight-grain float.
That's the easiest to make - you can get away with pine (the closer grained the better) although beech is flatter. Just use a piece of three-quarter or one-inch board and bung a handle on the back with which you feel comfortable. They wear out pretty quickly, so it's not worth doing fancy joinery unless you've got a good workshop and time on your hands.
Cross-grained floats are tricker because of their tendency to warp. You need to dovetail in a piece of hardwood with the grain runnng the length of the float to keep it straight, and the handle is bonded to that. For that you will need a bit of time, a good router and a good eye.
I've just bought a plastic one (well it came free with a watering can at a car boot). Havn't tried it out yet. I can see it may have the advantage of being much lighter than a wooden one.