I have recently done my first mosaic job, in my own bathroom. My house is a test bed to help me learn.
The key to mosaics is preparation. You need a flat surface with no lumps or bumps for the tiles to lie flat. It needs to be 10 times flatter and regular than a surface for say 6x6 tiles.
Bal do a product called Mosaic Fix. Some here think it's expensive and I think the Mapai equivilent is cheaper, but I can't get Mapai from CTD down here.
As kilty has said, the adhesive is quite good at holding them in place. The secret seens to be to put the right amount on to get full coverage and not a lot more, so you don't have an issue with grouting. If you get this right and press each tile home then the tiles will stay in place no problem.
One tip that Nick (Leatherface) told me when I posted my bathroom pick here, was to start from the top of the tiled area and work down.
Neale (Sir Ramic) also told me a good way to get them nesting nicely to hide panel joins. Remove alternate mosaics from each sheet where it buts up to the next sheet, so in effect you'll dovetail the sheets. Just keep an eye on the horizontals and verticals and it will work.
BAL Mosaic Fix has a long working time so you'll have plenty of time to do the job, so take your time.
One final tip I picked up here - when the tiles are fixed in place but before the adhesive dries off, use a small paint brush dipped in water to chean out the adhesive from the grout lines. I used a 1/2" brush that I cut short for this very job, works a treat.
When I last did a mosaic baorder I must admit I used a tubbed adhesive, as this was going on the walls anyway. It worked fine. I guess that you could use a good tubbed adhesive for mosaics in the right situation, but I would use a premium mosaic adhesive for my first job, or if I wasn't sure of my ability to work fast.,
