There are so many glues on the market at the moment that it is hard to know what to pick.
First things first are you will need to look at your surface and what tiles you are using.
Unfortunately, there is not one glue that does all surfaces. I have seen so many clients come to me with a glue they have used and its just a mosaic cement or mosaic adhesive, so generally, with the name mosaic next to it they assume it can be used for all surfaces, not correct!!
Let's go through the glue list!
Glass to Glass
Selleys Liquid Nail's Dries Clear
Is a Clear glue in a blue blister pack, available Hardware stores dries clear. This is a great glue to use but please use in a well ventilated room.
Prep Multihesive is a styrene acrylate, water-based multi-purpose adhesive, originally designed to replace PVA adhesives for all building and craft projects. Internal / External application Non-toxic Non-flammable Dries quickly – dries clear Non-flammable High water resistance and will not re-emulsify Made in Australia Prep Multihesive will bond almost anything to anything. Bond strength is greatest on porous surfaces such as timber, fabric, leather, paper, styrene foam, metal, wood and even concrete, plaster and fibro. Prep Multihesive is also a suitable adhesive for non-porous surfaces such as steel, aluminium, brass, copper, ceramics and glass. It will not re-emulsify nor dissolve if subjected to water after drying like PVA's. Prep Multihesive is a thicker emulsion than PVA's so it doesn't drip on vertical surfaces. It has greater bond strength on most surfaces. Prep Multihesive may also be diluted, for use as a 'dust sealer' or 'primer/sealer' for concrete and masonry surfaces. It may be used diluted as a bonding agent between layers of concrete or in the mix. Adheres to porous materials, e.g. timber, concrete, brickwork, ceramic, glass, wallpaper, canvas, carpet, fabric, leather, paper and non-porous materials, e.g. most metals and styrene foam.
Is okay but if you are after a crystal clear finish, for example for a sun catcher or tea light where you need the light to pass through, then Prep Glue is an inexpensive option can also be used on wood (My Choice for glass to glass).
Info: Weldbond is a non-toxic and environmentally glue, sealer and bonding agent all in one. This is versatile glue, is ever popular with mosaic artists around the globe and is user-friendly.
Ready to use
The many surfaces that can be glued make this an all-round fantastic glue, suitable surfaces include
Porus and non-porous surfaces
Drying time: Weldbond becomes tacky quickly and will dry within the hour, depending on temperature and humidity. It is fully cured when the bone is clear (transparent).
The longer it's left the stronger the bond.
You can also use as a Sealer before mosaic is applied: Use as a porous surface sealing agent, mix 1 part Weldbond to 5 parts water
Weldbond is weatherproof, not waterproof, I would suggest if using external only use on vertical surfaces and make sure your project is prepped and sealed afterwards.
Terrocotta, Concrete, fiber cement Sheeting, Wediboard
Thinset (Mosaic Cement) Mix with water.
Waterproof - recommended for outdoors.
Suitable Surfaces: Concrete, Cement, Renders, Plasterboard, Fibre cement sheets, wood backers
Cure time: 6-8 hours
Directions: All surface must be structurally sound, dry and clean.
Mixing: Measure a suitable amount for your project, a small amount at a time is a good idea as you do not want the adhesive drying out while you are working on your project.
Into a plastic container mix desired amount of cement with clean water, mix with a spatula for several minutes to ensure this is mixed together, once this forms the consistency of toothpaste, let stand for 5 minutes, then remix before using. Once tiling is complete make sure any excess adhesive that has oozed between tiles is cleaned away, a good way of doing this is with a soft-bristled toothbrush or paintbrush.
Applying Adhesive: This can be done with an icy pole stick for smaller pieces also you can make a small piping bag by using any small plastic bag, fill with the mixed adhesive and then cut a small slit in the corner and pipe out a small amount of adhesive, other than that you can spread the adhesive on with a notched trowel and arrange tiles to fit.
Glazed Ceramic Surface: Eg glazed pots and surfaces
We use liquid nails or Silicone. - just to note I do not use Liquid nails on mirror backed surfaces. Over time the glue can eat through the underside of the silvering
Definitely a silicone if the birdbath is glazed or if it is a porous surface you will need Thinset, just check with your local hardware store or marine supplier what is best if you are having fish in a pond it will have to be a marine-grade silicone.
External Weldbond is okay as long as the correct steps are taken to prepare your surface before and after. If I do use Weldbond outside it is only for vertical projects and I ensure my project is sealed beforehand and I also use a grout additive in my grout for extra waterproof and stability
PVA glue is good but a little runny strictly for interior projects
There are so many different comments about the right glues. It is a personal choice, taking into consideration the environment you live in. The more you prep your surfaces the better!
Always re-check and clean polish your exterior items every 3 months, check the grout is stable in the cracks and keeping them clean, they still need to be maintained and checked on now and again especially for extreme environments.