The perennial problem
What to do with leftover tile adhesive?
It must have happened countless times. You have a nice batch of tile adhesive mixed for a session at the mosaic table. It’s soft and yet firm. There is no water sitting on the surface and it is malleable to just the right degree. Then the phone rings. You can see it’s a) your mother b) your friend who’s going through a tough time or c) your child who’s meant to be somewhere where they shouldn’t be calling you.
Boom. Your session is cut short. But what do you do with the left over tile adhesive thinset*? I have to confess that I have often consigned it to the bin. Feeling guilty, I scrape out the now crusted tile adhesive and promise myself that I will be better organised in the future.
Ditch the bowls
However, over the years I have devised three ways to deal with the left overs. Read on to find three simple methods of using up thinset so that you never have to chuck it away again.
First, let me tell you about a clever little trick. Instead of using the traditional rubber bowls for mixing adhesive (see right), switch to cleaned-out yoghurt pots. Take the pot, cut it to half its depth and Bob’s your uncle. The great thing about using old yoghurt pots is that you can walk away without cleaning out the pot. The next day, it just needs a quick squeeze. The old tile adhesive easily cracks off and the pot is ready to use again.
Method One
Spread a thickish (5-7mm) blob of leftover thinset over a sheet of plastic. Leave overnight and in the morning it will be a hardened cake. You can then cut the cake with ordinary tile nippers to create tesserae which can be used in future projects.
Method Two
If you are a seasoned mosaicist you will have at least one jar (more likely, dozens) of offcuts that you fondly imagine will come in useful one day. As above, spread a blob of adhesive onto a sheet of plastic and randomly press the offcuts into the paste to create interesting shapes. These can be used as large tesserae another time.
Method Three
Have a simple mosaic on the go which you can build up using the leftovers. I have this one using a design loosely based on a Gees Bend quilt. Every time I have some spare thinset I can just add another row to the outside edge of the mosaic, building it up slowly over time. This 
method takes a bit of forward planning but, hey, getting organised is not beyond the realms of possibility!
*Tile adhesive and thinset mortar are exactly the same thing. Hardware shops and building suppliers supply the product for sticking down indoor and outdoor tiles. In the UK, we call it tile adhesive. In the US, it is called thinset mortar. The terms are interchangeable. To learn the secrets of using thinset, read Julie Sperling’s guest blog.Watch my YouTube video about using leftover tile adhesive.