Before starting that first mosaic project, the artist must decide upon the correct adhesive. Choosing the glue will insure that the mosaic will last forever. If you choose the wrong adhesive then be certain that your tesserae will not last long on the surface no matter where it is placed or how well it is prepared.
There are several types of adhesives. Each one works better with different surfaces and tesserae. Gaining a better understanding of these choices makes creating your mosaic more enjoyable and less worrisome.
PVA glue is simply a water soluble adhesive. It is easy to clean up by just using water. For this reason do not use a PVA glue on any project that will be kept outdoors. Even if the piece will be kept under a covered patio, the humidity will still affect the fortitude of the glue. So a PVA glue is only good for indoor use.
This glue has several uses in mosaic art. Mixing 1/5 PVA glue with 4/5 water, gives you a great sealant for wood surfaces. Simply brush on and allow to soak in. After it has dried then you can just mosaic on top.
This glue can also be used to tile tiles to fiberglass mesh in the double direct method. Use full strength but sparingly so that it does not completely cover your mesh. You need to make sure there is room for the final adhesive to get through to the tiles.
PVA glues can be used with any type of tesserae and are easily used on wood and acrylic surfaces. It typically comes in a squeeze bottle and is perfect for children since there is no odor. The most popular brand in mosaic art is Weldbond since it dries clear.
This cement based adhesive is the best glue for exterior projects. It typically comes in gray or white and can be tinted with grout colorants for self grouting pieces. There are several brands to choose from at your local hardware store. The only drawback is that you have to purchase it in large quantities of 25 pounds or more. Some mosaic supply companies offer thinset in smaller quantities for people that just want to try it out.
Thinset mortar is best used on cement, backer board, wood, and terra cotta surfaces. It bonds well with most porous surfaces. Do not use thinset on glass or metal surfaces as it will not adhere. This is the ideal adhesive for concrete stepping stones.
This adhesive can be very messy to use. The instructions state to mix this powder with water. However, it is highly recommended to mix well with an admix of either latex or acrylic. Admixes are a liquid that makes the thinset very sticky and easier to adhere to glass tiles and other nonporous objects. Only mix a small amount at a time. Once the thinset starts to haze over on top then you must throw it away. So mix just enough to cover a workable area of about 30 minutes. Do not buy the premixed thinset as it is not as good as working with the dry mix and admix.
Use gloves and a mask when mixing the thinset. Also use materials that can be discarded when mixing and working with thinset such as plastic containers, plastic spoons, old rags, newspaper. Once you finish just throw away everything. Do not try to reuse containers with thinset inside. Never wash thinset down a sink drain. It will stop up your pipes!
Silicone is perfect for adhering tesserae to glass and acrylic. It is typically clear and works great for placing transparent glass on a glass surface. Silicone is also rated for exterior use.
It usually comes in a tube or caulking gun. It is somewhat difficult to get used to working with though. Silicone tend to get stringy when being applied. Take care not to get it on top of your tiles. If you apply it too thick then it will squish up between your tiles and could lead to a mess.
Epoxy is the best adhesive for applying tesserae to metal. It holds up well outdoors and can be used with any type of tiling material. It can also be used on other surfaces like wood and glass.
Epoxy is difficult to use. It comes in a two part series. You have to mix each part together and use quickly. Only mix a little at a time or you will waste a lot. Benefits are that it is a very strong adhesive and it dries clear. This has a very strong odor so use in a well ventilated area.
There are many other types of adhesives that different mosaic artists rely upon. When you find a new glue, read the label carefully to make sure it will do what you need. Check to see if it is for exterior use, highly toxic, and what surfaces it can touch.
Some other brands that are well liked by many mosaic artists include Liquid Nails for Small Projects, MacGlue, and Gorilla Glue. If you are not sure about a new adhesive, then try a little on a small piece and see what you think.
Unfortunately you will learn that some adhesives are not good at all. Some make a huge mess. Once you find an adhesive that you like, then use it as often as you can.