Adhesive is an integral aspect of mosaic art. The first mosaics I made were stepping stones, affixing pebbles to concrete pavers with thin-set cement mortar. Thinset is finicky, like its cousin grout. Once the process of becoming cement begins, you’re on the clock. Adding more thinset to a soupy mixture or adding more water or admix to a bread-dough type consistency weakens the adhesive qualities. Thinset also has a memory, and once you stick a pebble down, the thinset won’t be happy if you move it. I learned to mix small batches in deli containers to reduce waste.
Then I took a class, and was introduced to Weldbond: Universal Space Age Adhesive. How could anyone resist that name? And for me, the fact it was from Canada was all the better, since I grew up in Alberta. Weldbond is not for stepping stones; it is water-soluble. But what a relief from thinset. Mosaic artists can have long earnest debates about adhesives(our mosaic-geekiness showing through), and tend to be loyal to different kinds. I am a Weldbond Woman. If I was primarily a garden artist, sign artist or maker of public art, I can see how I would be swayed by thinset, but I make mosaics for the home, mostly inside.
Weldbond is a non-toxic white pvc glue. It can bond just about anything and works well with glass because it dries clear. I like working with translucent and transparent glass, to let light in, and increase the glowing intensity of color, so I don’t want a glue interfering. It does require patience, as it can take a couple weeks to completly turn clear if you are applying glass on glass, and if you grout too soon, the air can’t get in to complete the process. But this is a fine trade-off for not having to open the window to air out fumes as with silicone adhesive. It sets up within the day, but I always wait at least 24 hours before grouting. The longer is sets, the stronger the bond gets.
I gave up on the small bottles, which tend to clog, and have ordered it online by the gallon from ACE(it’s mostly carried by independent hardware stores and online mosaic supply shops). I pour a small amount onto a plastic deli lid and either dip tesserae in using tweezers, my fingers, or spread the glue onto the substrate with a putty knife. It takes practice to know how much glue to apply. You want enough to coat but not so much that it oozes up between pieces, clogging up the groutlines.
If I really am troubled by a particular piece already glued down and set, I brush a little water around the piece, let it sit 5-10 minutes and lever it up with an awl or other sharp pointy instrument. Sometimes a bit of the substrates comes up too, but it’s manageable. Wear eye protection if you perform this operation, because glass can splinter when you apply force and it’s not fully loosened. I make it a practice to leave individual pieces alone, until there are enough of them glued down to see if anything is glaring, or interrupting the flow, and then, I still remind myself that it’s the total effect that matters, and if I get in a mood and pull up more than I glue, it’s still never going to be perfect.
A final bonus with Weldbond–if you leave a bit out on the lid, and it dries clear, you can pull the clear vinyl-like disc off in a most satisfying manner.