Since I am always being asked what adhesive we use at school for the direct method, today I would like to tell you about this.
If you you look at the photos I post in the section Spilimbergo 24/7 you see that we do not work directly in the mortar but our thin set is formed of an adhesive.
Huh? Yes. This cement adhesive is a powdered adhesive containing a high content of cement. At the same time the cement adhesive forms the mosaic surface.
We use the cement adhesive in combination with powdered brick and an elastifying latex dispersion (instead of water), which makes the grout more resistant to cold and stress. The mixture is therefore suitable for interior and exterior mosaics. The curing time depends on the ground and is about 2 – 4 days.
In school and in Italy in general a brand that starts with M and ends with APEI is ubiquitous. As we work almost exclusively here with their products, I am seduced to pass the product names to you unfiltered. But as I don’t want to be taken as their press agent, I’ll name you some products of two other manufacturers on the way. Depending on where you live, these are certainly to be found easier.
Mapei Kerabond (available in gray and white ) + Mapei Isolastic
More information at mapei.com.
Knauf Bau- und Fliesenkleber C1TE + Knauf Kleber- und Boden-Elast.
More information at knauf.de.
Laticrete Permacolor grout + Laticrete 4237 Latex
More information at laticrete.com.
Mix 1 part of latex dispersion with about 3 parts of cement adhesive until you receive a toothpaste-like consistency. The collar should neither be too moist nor too dry. It should shine but not be too liquid.
If you want to use colored adhesive just add color pigments or brick sand. But don’t exaggerate (don’t use more than 7 %), otherwise the adhesive ability is impaired!
We bath each tessera in the adhesive (using tweezers) and form an evenly closed mortar bed bonding together the little pieces and at the same time creating a base for the mosaic. The stones should be fixed about 2/3 in the glue – a bit like your teeth in the gums.
For processing of the adhesive you have about 8 hours time. When the glue starts getting dryer, you can stir it with a few drops of latex dispersion to make it smooth again.
Depending on the size of the mosaic, this should be reinforced in retrospect to a network and / or placed on a stable surface. See the next item.
Underground / stabilization of the mosaic
There are various possibilities to stabilize the mosaic created with the cement adhesive described herein.
Work directly on firm ground
The easier way: Your directly work on a stable surface. Suitable wood panels such as MDF work well for interior purpose. The very light and flexible honeycomb or sandwich panels are suitable for outdoor use. If the wood is too smooth, you can carve it with a cutter before placing the mosaic.
Provisional underground with subsequent fixation
This is how we work mainly: Either 1.) on a glass fiber net in an appropriate mesh size (depending on the size of the tesserae you want to use). The net (under which we lay a a nylon as non-adhesive base), together with the cement adhesive forms a solid surface. Even if the mosaic breaks its parts will stay together. Or 2.) work directly on the nylon foil (polyethylene). The mosaic dissolves from the nylon after drying.
The final mosaic is glued to the solid base. For this purpose you can also use the cement adhesive described here.
You have questions or comments? I look forward to receiving them!