I am installing mosaic tile backsplash for the first time. Since I know I'll be slow and I have 3 sections of wall to do, I want to know the best way to divide/calculate the thinset I bought so I don't mix up more than I can use at one time. Bag instructions only show mixing up the whole bag. Any ratio suggestions i.e 3 cups thinset to ?? oz of water

If you're setting mosaic tile on a back splash, my advice would be to use a mastic instead of thin set. The reason why is that mastic is both much more viscous and it has a stronger initial grab, so the tiles won't "sag" as much as if you set them in thin set.

The problem with using thin set to set mosaic tiles is that in order to have a longer working time and have the thin set "wet" the backs of the tiles, you need to mix more water into the thin set. The problem is that the more water you mix into it, the more the tiles are going to sag as the thin set behind them sets up. With wall tiles you can prop them up with spacers to avoid that sagging, but you can't be starting to set 128 spacers in every sheet of mosaic tiles to support the 64 tiles on each sheet.

Mastic is clearly a better choice here because it's not really a wet area, and mastic will prevent the tiles sagging MUCH better than thinset will.

I've only set mosaic tiles in thin set on a horizontal surface once in my life, and I found that I had to "straighten" the rows of tiles in both directions with a straight edge because the backing wasn't holding them in position relative to one another. You're going to have even more of a problem with that on a vertical surface.

If you're still wanting to use thin set, then a good thing to do is visit any place in your area that repairs small kitchen appliances and ask if they have any kitchen mixer blades in their garbage can they can give you. If they don't have any just then, ask them to save up a few for you. Kitchen mixer blades have a slot in the back end that is turned by the appliance. That slot eventually gets stripped so the blade is no good anymore for use in a kitchen mixer, but it'll still work perfectly well in a variable speed drill.

Now, head down to your local 7-11 store and liberate as many Big Gulp cups as you can out of the garbage bins there. Rinse them out, and that's what you'll use along with a kitchen mixer blade in a drill to mix your thin set. You stack two cups together for better rigidity and add some water into the top cup. Use a scoop (which you can get cheap at any restaurant supply store) to add thin set to the water) and mix until you get a thick slurry that will still stick to your finger if you touch it. Do your mixing inside a tall cardboard box or 5 gallon pail so as not to get thin set flying all over the place from the mixer blades.

Mixing thin set is very much a "play it by ear" thing. You want the thin set to have enough water in it that it wets the wall and tiles well, but no so much that the V shaped trowel notches don't hold their shape after applying the thin set. So, it's really a learn-as-you-go kinda thing. A bag of thin set is more than enough to tile a whole bathroom, so you have way more than enough thin set to experiment a bit with on how much water to use with how much thin set to get the mixing ratio about right. You want the thin set to hold it's "V" shape ridges when applied to your wall, but still stick to your finger if you touch it.

Once you use up the thin set in the top Big Gulp cup, pull off the bottom cup and stick it in the dirty top one and you again have a rigid mixing container with a clean interior ready for the next batch of thin set. You can also use smaller kitchen mixer blades in empty soup cans for this purpose, or for that matter, ANY mixing container provided you clean it after each batch of thin set. I prefer to use mixing containers that will be going into the garbage anyway cuz it's less work for me.

But, here you really should be using mastic instead of thin set anyway.

Don't really know if this answered your question.

This message has been edited. Last edited by: Nestor,

What I have done is to use a postal scale to weigh the bag. Say it weighs 4 pounds and requires a quart of water. I might mix up 1 pound with 1 cup water then. That does work.

I'm not commenting as to whether this is the right product, but just a method of "cutting down the recipe"!

Call me simple but why not just mix up what you need and save the rest in the original bag?

Mixing guidelines on the bag are simply that - guidelines. Your mix ratio will vary depending on what you need for your tile (tile size, wall or floor etc). You mix ratio will even vary from day to day depending on humidity. This is not rocket science - once you have one or two tile jobs under your belt you will recognize the 'feel' of the thinset as you mix and can add water or more thinset to get the mix you need. This is also not a brownie mix - adding xxx amount of water to xxx amount of thinset is only a starting point - the mix will not be ruined if you vary from the printed instructions to get the consistency you need for the project.

BTW, Nestor is correct: Use a mastic for a mosaic backsplash. This will not only make for a better and easier tile install but solves your original mixing question too.

This message has been edited. Last edited by: Jaybee,

My guess is that the original poster isn't responding because the original question of mixing smaller quantities of thin set is no longer an issue. He's deciding what mastic to buy.

quote:

Originally posted by Nestor:
My guess is that the original poster isn't responding because the original question of mixing smaller quantities of thin set is no longer an issue. He's deciding what mastic to buy.

Hopefully. Watching perfectly set mosaic tile start to slide downhill is not my idea of fun.

ooh, Jaybee, you just described a Day Of Horror in our basement shower. I had no trouble putting on the ceiling tile. then we went to the wall. fourth course started a total nightmare.

never happened before.

Lord willing, never again.

but they look pretty good after using multiple Words Of Command... .