Adhesives for
Mosaics
When making a
mosaic, it is important that all three components; the mosaic materials, the
substrate (surface the mosaic is attached to) and the adhesive are all
compatible with each other and appropriate for the siting of the mosaic. For
instance, some mosaic materials such as china and substrates such as wood are
more appropriate for indoor use. Adhesives are also rated for indoor or outdoor
use. There is no one answer to the “which glue do I use?” question.
Adhesives are rated for different uses such as indoors, outdoors, horizontal,
vertical and submersible. It is important to choose the right one for your
application
PVA Glues
(white glues)
PVA glues
such as Weldbond, Selley’s Aquadhere etc are easy to use, dry clear and are
non-toxic. However, as they are water soluble, they are not suitable for
mosaics which will go outside or live in very wet areas. They are good for
indoor pieces and also for when using the direct method with fibreglass mesh.
Cement-based
adhesives
These are
usually suitable for outdoor use. They come in many brands and tile shops often
have a good variety. They are available in powder form, and usually in either
grey or white. Some are mixed with water, others are two-part and are mixed
with a polymer-fortified latex additive to give them flex and strength. The
pre-mixed ones are usually not as good as the ones you mix yourself.
Cement-based adhesives can be coloured with oxide powders, but it can be
difficult to maintain consistency over many batches. Some people use acrylic
paint but this is not recommended as it can weaken the mix and may fade over
time.
It is important to
choose the right one for your application, some are rated for outside use, some
for both horizontal and vertical applications and some for submersible ones.
There are various reputable manufacturers available in Australia
including Ardex, Mapei and Laticrete. Laticrete Gold, Mapei Kerabond with
Isolastic additive, Ardex Optima and Ardex X77 are among those which many people
use for mosaics. As different adhesives are rated for different purposes,
we would strongly recommend that once you have identified what
you would like to use, you check the technical data sheet on the manufacturer's
website to see if it is suitable for your purpose, or ring the manufacturer's
technical support line.
Note: Cement based
adhesive that can be laid in a thin bed are called “Thinset” in the USA and this
term is often used in mosaic books.
As well as
adhering the mosaic to the substrate, cement based adhesive can be used to cover
the sides of marmox board, and also for putting a skim coat over the face of the
board if required.
Ratings
Cement-based
adhesives are rated for specific uses. Eg; one might be rated for use with
ceramic tiles for internal vertical use, but not for outside horizontal use. So
you could use it inside on a wall but not outside on a floor. Ratings will
also tell you whether the adhesive can be used in a wet area, such as a shower,
or for submersible use such as a swimming pool.
Grout
Normally,
grout has no adhesive qualities and is just used to fill the gaps. However,
several manufacturers including Laticrete and Davco produce additives which turn
cement-based grout into a cement-based adhesive giving you an instant coloured
adhesive if you use coloured grouts.
Slaking
All
cement-based grouts and adhesives need to slake before using. This is a rest
period which can be from 2-10 minutes depending on the brand which allows the
chemicals in it to interact with one another before use. After the "slake"
period remix slightly then apply.
Other
Adhesives
There are
other adhesives such as two–part epoxies and silicone based glues. These can be
tricky to work with and may also give off fumes. Not suitable for beginners.
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Smalti Australia is based in the lower Blue Mountains west of Sydney. Visits by appointment. Tel: 0400 150 157, email:
info@SmaltiAustralia.com
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