Adhesives (or Glues)
GLUES:
We all have our favourites. There are many adhesives available to the mosaicist. I prefer using glues that can handle most situations, so do not recommend indoor only adhesives (for example). I also prefer to support Australian products where I can.
PVA (Poly-Vinyl Adhesive) :
- Suitable for indoor only – will re-emulsify in water or humid conditions.
- Solvent is Water
- White when wet, but dry clear.
- Common brands are Weldbond (Canada) or Selleys Aquadhere. Aquadhere is much cheaper. Unfortunately, whilst developed in Australia, Selleys is no longer Australian owned, but is part of the Dulux group (under Japanese ownership).
- Available from most hardware stores.
- PVAs can be diluted and used as a wash to minimise the effect of Grout Bleed.
MAC :
- An American glue developed by an artist specifically for Glass-on-Glass mosaic.
- solvent
- Pre cure – Water
- Post cure – No known solvent. Removal is via manual means (aka sharp blade). Heating with a hair dryer helps, and acetone seems to soften it, although it is still very difficult to remove.
- White when wet, dries clear.
- Use sparingly, do not shake.
- At time of writing MAC are experiencing difficulty sourcing a major component of the glue. Until a suitable replacement is found, MAC is not in production. Treasury Road (Australia) currently does have very limited stock.
- Does not tolerate low temperatures when wet
- Not stated as neutral curing, but anecdotally it is once dried. Waterproof once cured.
PREP MULTI-USE ADHESIVE :
- an Australian Styrene glue
- Solvent
- Pre cure = water
- Post cure (48 hours) = acetone (nail varnish remover).
- Weather Resistant.
- White when wet, dries clear.
- Environmentally friendly
- Non-toxic, non-carcinogenic
- Non-flammable
- High water resistance
- Will soften after prolonged exposure to moisture.
- Can be diluted with water and used as a sealant/bonding agent.
- Neutral curing.
- Sold by Merlin Mosaica, and Mitre 10.
- Can be used as a treatment against Grout Bleed. Once fully dry, the grout will soften the residual film which should come off during grout clean up.
CEMENTITIOUS ADHESIVE :
- Known as Thinset in the US (and on many Facebook mosaic sites). Also known as Tilers Cement.
- A cementitious powder mixed with either water or a latex liquid (Admix) for added strength.
- Solvent:
- Pre-Cure = water removes it. Best left for an hour or so, then easily wiped off with a spatula (really fresh and it will smear).
- Post cure = an acetic mix (dilute vinegar or muriatic acid – wear gloves) helps. A scrub with a wire brush can also work. Dredge the adhesive in water first.
- Use a mask when working with the dry powder.
- Some are rated interior only, and some are for porous tesserae only (i.e. not glass).
- Not advised for use on MDF, timber, acrylic or glass substrates. Comes in grey or white, can be coloured with cement pigments/oxides.
- Not neutral curing, so cannot be used for mirror or Van Gogh glass.
SILICONE :
- Many brands (Sika, Parfix, Selleys). Readily available from most hardware stores.
- Solvent:
- Pre Cure = Isopropyl alcohol (found diluted in some wet wipes) works on UNCURED glue.
- Post Cure = manual means (a sharp blade) or a specialty remover. I find the Soudal Sealant Remover & Silicon Remover Kit to be really effective. These 2 products have the same effective ingredients, but one is aerosol, and the other a paint on. Merlin Mosaics sells both of these currently, but I won’t restock the spray – I avoid shipping aerosols if possible.
- Usually supplied in a caulking tube for use with a Caulking Gun.
- Silicone contains toxins that continue to be off-gassed during the curing process.
- May be harmful or irritating to those with chemical sensitivities.
- Use in well-ventilated areas.
- Usually waterproof, but not always submersible.
- SOME are neutral curing.
POLYMER :
- A less toxic option to silicone.
- Solvent:
- Pre Cure = Isopropyl alcohol (found diluted in some wet wipes) works on UNCURED glue.
- Post Cure = manual means (a sharp blade) or a specialty remover. I find the Soudal Sealant Remover & Silicon Remover Kit to be really effective. These 2 products have the same effective ingredients, but one is aerosol, and the other a paint on. Merlin Mosaics sells both of these currently, but I won’t restock the spray – I avoid shipping aerosols if possible.
- Handles pretty much the same way as silicone but is much less harmful.
- Neutral cure adhesive.
- Manufacturer does not advocate use in submersible situations, BUT this concern is mitigated by the use of a suitable waterproof grout with no gaps. I recommend Epoxy Grouts in these situations.
HEAT ACTIVATED MOSAIC FILM :
- This is a specialist adhesive which I sell at Merlin Mosaica.
- Suitable for inside or exterior use.
- Submersible and neutral cure.
- Not recommended for highly curved or 3D substrates.
SUBMERSIBLE or NOT SUBMERSIBLE??
Many glues are not rated as waterproof, or are not recommended for submersion. However, the manufacturers are not usually considering the use of a grout layer.
The majority of mosaics that are likely to be submerged (think bird or bee baths) are GROUTED. If a waterproof grout is used, AND all joints and edges are fully covered, with no cracks, then the range of glues that can be used successfully increases.
What is NEUTRAL CURING, and why is it important?
All adhesives release chemicals as they cure, even a simple water-based one (after all, water is a combination of 2 elements – hydrogen & oxygen).
Neutral cure adhesives release a non-acidic substance while curing (unlike acetoxy caulks which release acetic acid). This is less likely to damage sensitive surfaces and substrates. For example, neutral cure is gentle enough not to discolour natural stone or corrode any metals.
In mosaics, this is particularly important when working with mirror. Mirror is glass that has been treated on the back face with a reflective film. Mirrors are produced by the wet deposition of silver, or sometimes nickel or chromium (the latter used most often in automotive mirrors) via electroplating directly onto the glass substrate. Glass mirrors for optical instruments are usually produced by vacuum deposition methods. So, it is important to protect this film from the corrosive effects of acetone or other acidic substances.
Don’t forget, mirrored tiles are often made the same way.
NOTE: Van Gogh glass is glass treated with an automotive paint. To my knowledge, it should also be used with a Neutral Cure adhesive.
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