Thinset Mortar for Mosaic Artwork
This page explains how to mix and use thinset bonding mortar for detailed
work with glass mosaic tile and other tesserae.
I. What Is Thinset And When To Use It.
For outdoor and wet mosaics,
thinset is recommended instead of adhesives. Thinset is a bonding mortar, which
means it is a concrete with polymers added to make it sticky and extra strong. This is
particularly important when working with glass mosaic tile, which is non-porous and
difficult to bond securely.
We use Versabond brand, which we buy at Home Depot, but you should ask at your
local building material store what they recommend for your area. (This could be
important if you live in a cold climate, and something else is being used by
your local contractors, but I suspect it is the same.)
II. Mixing Thinset
The thinset package has mixing instructions, but
these are written for mixing the entire package. For detailed mosaic artwork,
you will probably want to mix 1 to 3 pounds at most. You can find what
amount of water to add per pound by dividing the amount of water recommended for
the entire package by the weight of the package.
For Versabond thinset, we add
1/2 cup or 4 oz of water per pound. You can use that same ratio of 1 part
water to 4 parts thinset to mix up tiny batches of thinset, such as 1 ounce or
water plus 4 ounces of thinset.
We use a plastic measuring cup for measuring the
water and a small kitchen scale for weighing out the thinset, which we scoop out
with a small gardeners shovel or measuring cup instead of pouring.
Dust is an issue, so we wear a dust mask and keep a spray bottle for misting. We
also recommend doing the weighing and mixing outside.
For small batches of 1
pound or less, we mix it up in a 32-ounce plastic yogurt container and use a
putty knife or old butter knife to stir. For larger batches, we mix in a
5-gallon bucket so that we can mix vigorously without slinging out any material.
A smaller bucket (2 gallon) can also be used.
Note that you have to add the
water gently and mix slowly at first to avoid stirring up the dust before the
powder is wetted. Use a clean paddle or stick to stir. You will
notice that it takes some strength to mix up larger batches, and something more
sturdy than a paint paddle may be required. We have a mixing attachment
that fits into our electric drill for batches of 5 or more pounds.
mortar until it has the consistency of dough with no lumps. Take care to mix all
the way to the bottom of the bucket and scrape the edges to make sure that no
powder, lumps or clumps remain. Then the mortar is allowed to sit for 5 to 10
minutes, and then it is mixed some more.
After that, we mix in concrete dye if we
want to color the thinset. Typically we use Charcoal colored concrete dye to darken
the thinset, and we use it in much larger quantities than recommended. Most recently,
we added about 5 ounces to 1 pound of thinset without weakening the strength as far as
we could tell, but we make no guarantees about that.
Here is a list of items recommended
for mixing thinset:
- bucket or plastic container.
- dust mask
- small kitchen scale or postal scale
- measuring cup or large spoon or small gardeners shovel
- paint paddles or a small board for mixing
- spray bottle for misting
III. How To Use Thinset For Detailed Mosaic Artwork
Thinset is extremely
sticky and meant to be spread with a trowel to mount large tiles or sheets of
tile. How do you use it for "one-tile-at-a-time" artistic mosaic work with small
tiles without making a mess?
A small trowel or painter's pallet knife or butter
knife can be used to smear the thinset in small patches, and then the tile is
pressed into that similar to a normal tiling job. Or you can put a small amount
of thinset on the back of each tile, one tile at a time. Either way, you will
need a way of keeping your hands clean and a way of cleaning up random drips.
We use the following materials to keep the work clean and efficient:
- small plastic lid or tray
- putty knife or old butter knife
- painter's pallet knives if available
- spray bottle
- dirty rag
- wet rag floating in a bucket 1/4 full of water
- clean rag
- medical examination gloves (optional)
- old work surface or shop table.
- wadded newspapers in garbage can
The plastic tray or tupperware dish holds a
small amount of thinset for dipping the backs of tiles into. Scoop a small
amount of thinset into the tray and keep the rest of the thinset in the bucket.
Keep the bucket covered and use the putty knife to scrap the sides of the bucket
so that all the thinset is in a blob and doesn't dry out. Mist the thinset
sparingly if you see it drying. We can use thinset for up to 4 or 5 hours this
As you dip the backside of the tile into the tray of thinset, you will
occasionally get some on your fingers. If you are sloppy in how you clean your
fingers, you will use up tons of rags. Use this procedure to use only 3 rags:
- Scrape fingers off on the wadded newspaper in the garbage can.
- Use the DIRTY rag if needed, but try to use as little as possible.
- Dip fingers in bucket of water with WET rag.
- Use the CLEAN rag to dry fingers.
Whether you spread the thinset in
small patches or put a smear of thinset on the backside of each tile will depend
on your style and pace of work. If you are improvising your design as you go
along, you may find that you use both techniques.
For found object mosaic, we
sometimes use a grouting bag fitted with a Wilton brand cake icing nipple. The grouting bag with nipple allows us
to dispense the thinset in a very controlled way as if from a bottle of
glue. This technique can also be used for flat tile.
We use a rubber band to help hold the plastic collar over
the metal nipple of the grouting bag