How To Make Mosaics

The ”Indirect Method of Making Mosaics” is completely different in concept to the “Direct Method“. The basic idea here, is to split the work of setting up your mosaic into two stages. The first stage involves setting up the tesserae (mosaic tiles) onto a temporary base, before actually cementing the tiles into their final position on the mosaic itself.  There are several variations to this method, but all of them involve initially setting up the mosaic tiles (tesserae)  in a reversed (upside down) configuration in a temporary work area, away from the final location. 

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The Advantage of the “Indirect Method” is Threefold: -.

•  Firstly, it is a way to get a truly flat (plane) surface for projects such as table tops and bar counters – this is always difficult to achieve using the direct method.
• Secondly, much of the labour intensive part of the of the mosaic project can be done indoors, away from the actual final location of the mosaic, which could be exposed to the elements or in a busy thoroughfare. 
• Thirdly nearly all of this preperation work can be done working horizontally on a table top or workbench – even for a wall mosaic. It is much easier setting up a mosaic horizontally. 

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Method 1: Reversed Cards of Tesserae

•  You start off by creating a temporary “sheet” or “card” of inverted mosaic blocks, using stiff craft paper or other suitable material. This sheet or “card” is first prepared by tracing a reversed mosaic pattern of your design onto a temporary backing sheet of craft paper.  The reversed pattern is in effect a true mirror-image of the actual mosaic design as it would look, once completed. The sheet  is then stretched out and pinned or taped tightly down to a flat working surface such as a kitchen table.

• The next step is to use water soluble glue to paste each individual mosaic piece (tessera)  upside down onto the backing paper, while religiously following the guidelines of the inverted pattern.  N.B. –  the tesserae are pasted with their bright side against the craft paper and rough side facing up. On completion of the temporary gluing operation, you will have a flexible “sheet” of prepared mosaic tiles. If the mosaic is too large to be comfortably handled in one piece, the backer paper may be cut into manageable portions. Carefully mark  references onto each segment so that you can recall the  sequence and orientation of them relative to each other, as you will later have to reassemble the pieces by fitting them back  together onto the mosaic, in the manner of a jigsaw puzzle. Bear in mind that at that later stage, because of the overlying paper, you won’t be able to see the faces of the tesserae and you will essentially be working blind, with your reference marks as your only guide – so give this aspect your most careful attention.

• Once the water-soluble glue has set and you are sure that all the tesserae blocks are all firmly bonded to the craft paper on each of your “cards”, you can stack them away and prepare to start work on the actual mosaic itself.

• Roughen up the surface that is to receive the mosaic with a wire brush (or chipping hammer if necessary), then  spread your tile cement or adhesive in a fairly thick layer over it.  You should use a notched trowel for this, so as to get an even thickness of paste. The adhesive or cement should have the consistency of a fairly stiff, but still creamy paste that is not at all runny or lumpy. 

• The ”cards” of mosaic tiles that you have made can now be turned over and the exposed rough faces of the mosaic tiles are pressed a little way into the adhesive – just enough to hold them secure. A piece of flat board or plank  should be now be used to gently tap your “sheet” of  tiles home into the  bedding adhesive, as this will ensure that the upper (papered) surfaces of all the tesserae are properly aligned and the individual blocks are brought flush with each other – i.e. the final exposed faces of the tesserae will all be set in one flat plane. 

• After the bedding adhesive has set and been allowed to cure for a couple of days, the craft paper is rubbed off with warm water. Grouting can follow immediately thereafter.  

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Method 2: Concreted Tesserae Slabs

This application of the “Indirect Method” is similar to the “card” method, but instead of pressing the mosaic tiles on their cards into the cement paste, in this instance, concrete is poured over the tesserae to make “facing slabs” or “mega-tiles” that are in turn cemented onto the underlying concrete floors using normal  tiling techniques.

• As before, you make a full-scale ”mirror-image”  paper guide pattern of your entire mosaic project. Divide your pattern into equal sized rectangles (or squares) and cut the pattern into these segments.

• You then construct a shallow timber mold box that has the exact dimensions of the pattern segments (make several identical boxes if the mosaic is very large). Each segment of the pattern must fit precisely within the mold. Glue  or pin the pattern onto the bases of the molds.

• You are now ready to paste the individual tesserae down onto the pattern, using  water soluble glue. N.B.  – the bright faces of the tiles must be kept downward and the rough sides up.

• When you have completed the pasting of the tesserae onto the paper, carefully pour a small amount of reasonably fluid cementitious grout around them to about half their height - this can be coloured grout, if  prefered. Leave for about an hour for the grout to set and bind the mosaic tiles, but not longer.

• You  now gently fill up the remainer of the  mold with a  fairly fluid (workable) concrete topping. Compact the concrete by tamping it down softly with your trowel. Remove any excess concrete and float off the top of the concrete to give a good level surface. The concrete will need a few days to cure and harden, before it can be removed from the mold as a “paving slab”. Repeat the action for the other elements of your mosaic design. Once they have set, the slabs should be kept damp while curing, as this increases the strength of the concrete.

• When you have cast all of the individual portions making up your mosaic and the slabs have cured sufficiently, they can be turned over and have their top (mosaic) surfaces cleaned of glue, paper and excess grout. They must be laid out against each other and checked for consistecy of pattern and shape and at the same time inspected for  minor flaws and repaired as necessary.

• The slabs are now ready to be cemented down onto the underlying concrete base. While doing this, take special care to keep the upper faces of the slabs perfectly level. If  it is acceptable to you, you can just pack your slabs tightly together (jigsaw style) – thus leaving minimal joints for grouting up. This could well suit a purely geometric mosaic design. However to maintain the “flow” of the tessarae within in a more complex piece and to disguise the jointing, it is much better to plan from the very beginning  to leave fair sized strips as unfinished gaps between individual paving “slabs”. These strips can then be tied in, using the “Direct Method”, i.e. – finish off  the floor by embedding the missing (linking) tesserae directly into  mortar beds placed within the gaps and then grout up in the normal way to complete the job.

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Method 3: Casting Tesserae Table Tops

It doesn’t take too great a leap of the imagination to see that the above method can easily be adapted to make table tops and similar panels in just one simple operation. All that is needed is for a single mold, big enough for casting the entire unit in one operation. The “paving slab” in this case would be the complete finished product. The only problem is going to be  the handling involved in turning over and placing the unit as it will be very, very heavy.  Be sure to use very high strength concrete -  3:2:1 (i.e. 3 measures of stone, 2 of sand and one of cement) and cure it properly by keeping the unit moist at all times. Sprinkle with water and cover with some plastic sheeting.

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