A modern technique, usually called the “double indirect method”, is used for both artistic and commercial mosaic applications. The double indirect method allows for numbers of the  mosaic tiles or tesserae to be pre-assembled on a sacrificial backing mesh and made up into convenient  sized portions or “cards”. These made-up units can then be further combined together to make up the ultimate  mosaic display.



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Commercial Applications

Double Indirect Method for a Small Home Project

Double Indirect Method for a Large Project

Commercial Applications

The Double Indirect Technique is the most generally accepted method used for  mosaic tiling of showers, bathrooms, swimming pools and other bulk mosaic work. The factory made “cards” of mosaics on their mesh bases are both economical and practical and are extensively used on most modern building projects. For these  commercial applications of the Double Indirect Method, individual mosaic tiles are sorted in the factory and assembled into various popular patterns and  styles and are then permanently glued onto a base mesh of tough synthetic material, with the face side of the tiles always uppermost. These prepared cards of mosaic tiles are either sold individually or in sets. The cards are usually square or rectangular and are thus easy to handle and can be set into  position in much the same way that ordinary patterned tiles would be. The tiler simply places them onto the surface he is covering,with the bright side up, and they are  pressed down as individual units directly (mesh and all) into a prepared bed of adhesive and leveled off, ready for grouting.

As already noted, the Double Indirect Method is not restricted solely to commercial applications,  as an adaption of  this technique is often the most appropriate choice for an artist with a commission to fulfill for a larger original work – especially where there are good reasons for keeping the actual site work to a minimum. Moreover there is also a simple application of the technique that has several advantages for the hobbyist who is willing to try out an alternative method for smaller home projects.

Double Indirect Method for a Small Home Project

  • The first step is to cut two sheets of stiff cardboard or plywood to the exact size of your project. Pin one of these boards to the workbench and cover it with grease-proof paper. Paste or scribe your design pattern onto the paper, so that you have a guide to work to and place it on a flat work surface.
  • Next, lay out the mosaic tiles (tesserae) directly onto your pattern, with the bright side facing up,  until the entire board has been covered by the tesserae and has the appearance of the final work, just as you envisaged it.
  • Working with short strips of clear parcel (packaging) tape, carefully tape over the entire upper surface of the mosaic tiles, making sure that the tape adheres firmly to each individual tesserae piece. This must be done  without disturbing the relative position of the tesserae. Use clear rather than opaque tape, as this will allow you to see if any tesserae get dislodged in the process and need adjusting.
  • Once you have covered your entire mosaic with tape and the tesserae are all firmly held in position, lay the other cardboard sheet over the top of the mosaic and tape the two boards together at the edges. You now have your mosaic sandwiched securely between the boards. Get someone to help you gently rotate the boards until your mosaic is now laying upside down, with the rough underside side of the mosaic tiles now facing upward.
  • Carefully cut away the upper cardboard, exposing the underside of the tesserae. Take a sheet of strong  fibre glass mesh (or other synthetic fibre such as polyester) , that has a fairly open weave but is tight enough to contain the tesserae . Stretch this mesh tightly over the entire work and maintain the tension by taping down the edges of the mesh directly onto the work surface with your parcel tape. There must be no ripples or slack in the mesh.
  • When everything is secure and tidy, use a paint brush to glue the mesh directly onto the inverted mosaic tiles. The glue that we use for this is usually a “two-part ” glass fibre or epoxy resin. (Tip – be very careful to use the resin sparingly or you will have a right old mess on your hands). Acetone can be used to clean up smudges or spillages. When the resin has set, you should be able to lift up the whole assembly as a semi flexible unit.
  • Leaving the tape in position, rotate the  assembly so that the mesh is now on the underside. Cement or glue it into its final location by pressing it into a thick bed of your chosen tile adhesive. Use a board or plank to level off the tesserae as you press the mosaic into the bedding paste to ensure that the end result is a truly flat surface.
  • When the bedding has fully hardened, you can peel off the parcel tape and grout up your mosaic. The residual stickiness left by the parcel tape is cleaned off with methylated spirits or acetone (not turps which could stain the grout). Try cleaning just a small corner at first, to make absolutely sure there is no staining

In lieu of the parcel tape, it might be cheaper to paste on craft paper over the tesserae, using a water soluble glue that can be washed off prior to grouting, but this is more trouble and will take a lot more time.




The Double Indirect Method for a Large  Project

The Double Indirect Method  is also a very convenient technique for the mosaic artist who needs to set up an original work on a large scale. The planned mosaic may be destined for an outdoor project and thus subject to weather constraints or otherwise destined for a busy public location, where  the daily bustle  could distract the workflow. The  advantage of the Double Indirect Method is that virtually the entire mosaic from concept to completion can be pre-assembled away from the site, in the artist’s workshop or studio.  The quiet of a well laid out studio will always be  a more suitable place to carry out creative work. There are less distractions and there is the benefit of more controlled conditions and better facilities. 

  • To start off, the artist should prepare a flat working surface large enough for the entire project – or at least sufficient for a substantial portion of it. This work surface would be covered  with a bond-breaking sheet of grease-proof paper or something similar. This is necessary to prevent bonding with the glue we are going to use to hold the mesh.
  • A scaled-up pattern, extrapolated from the artist’s original sketches, would then etched onto unto the bond-breaker paper, to provide guidance in placing the mosaic tiles (tesserae). 
  • A synthetic fibre mesh (usually glass fibre), is then stretched tightly over the work surface and should cover the entire bond-breaker paper. The interstices in the mesh must be suitable for the size of mosaic tiles you are going to use and the individual strands shouldn’t be too thin.
  • Working with just a small part of the pattern at any one time, it is preferable to use a crochet hook to lift up sections of mesh slightly above the paper while you are smearing the fibres with glue. This is to avoid getting too much glue onto the grease-proof paper underneath. The glue that we use for attaching the mesh to the tiles is usually the common “two-part” polyester glass-fibre resin.
  • The tesserae can now be placed directly onto the glue-soaked  mesh in accordance with the design pattern. Don’t dab any of the resin glue onto the underside of the tesserae themselves as you want to keep these surfaces clear for the final bonding with the tile bedding cement. (Tip – be very careful to use the resin sparingly or you will have a right old mess on your hands). Acetone can be used to clean up smudges or spillages.
  • Once the entire mosaic, or maybe just a fair sized segment  of the project, has been set up to the artist’s satisfaction and is adhering firmly to the fibre glass, the mesh  will be carefully cut into smaller, more manageable portions to make up “cards” of mosaic tiles for transportation to the final location. Before the “cards” are lifted off the work surface, the upper surfaces of the mosaic tiles are taped over with clear packaging tape or an adhesive film to prevent the top surfaces from getting dislocated or distorted, while they are being handled.
  • The separated cards are then each marked with an identifying number and orientation lines and are photographed in situ, before being lifted of the bed. They are then carefully turned over and inspected, if necessary, the glass fibre mesh can be re-glued to any loosened tiles. (Note – make sure that the resin doesn’t block up the interstices of the mesh)
  • When the entire mosaic has been reduced to a stack of “cards” it can be taken to the final location for assembly. Using the photographs for reference, the artist and his helpers will then be able to insert the “cards” of mosaic tiles as pieces of a gigantic “jigsaw puzzle” to reassemble the mosaic into its final position.
  • It is important that the “cards” are aligned very carefully against each other before being gently pressed down into the prepared bed of  adhesive. It might actually be better to remove the tape or adhesive film beforehand, if this makes the alignment easier.
  • The bedding adhesive or cement should just fluid enough to flow easily through the interstices of the mesh to ensure a good bond to the tiles themselves.
  • When the glue has set, all that remains is for the mosaic to be grouted up and prepared for viewing.

(Tip – please don’t get too ambitious at first! There is actually a quite a lot to learn if you are to master this technique properly and you  should try out  the details of your proposed methodology on one or two small trial pieces before embarking on your first major project). You will need considerable  practice if you are to get this method right first time.

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