Many mosaic enthusiasts ask about making starch glue for the Indirect method working on paper, here Gary shares his recipe…
The indirect paper face method of making mosaics is very versatile and simple and is used for making mosaics large and small, including the largest mosaics. The glue used to stick the tesserae to the temporary paper support has to be strong but water soluble so it can be removed when the mosaic is in situ. The best glue to use for this purpose is a flour and water paste, known as Pasta Amido.
Interestingly many mosaic studios have their own recipes for this making starch glue, often closely guarded secret recipes. Each studio adding extra ingredients usually either to extend the pot life, adjust for local conditions or increase the stickiness. However the basic old recipe is perfectly fine in most situations and it’s the one I have been using for over twenty-five years. The following is the method I usually use followed by the original recipe from the great renaissance work on materials and techniques of artists ‘Il Libro dell’arte’ by Cennino Cennini.
Pasta Amido (Mosaic Starch Paste)
- In a saucepan mix a tablespoon of flour with just enough cold water to make a paste the consistency of single cream.
- Add a tablespoon of salt (this helps delay the glue going off – see below)
- Very very slowly add boiling water from a kettle stirring constantly to avoid lumps.
- Put the pan onto a gentle heat and whilst still stirring bring the mixture slowly to the boil.
- The mixture needs to be about the consistency of double cream but can range from ‘single cream’ for fast papering of vitreous tile, to a thicker paste for marble tesserae.
- If the mixture gets too thick simple add more water. You must keep stirring to avoid lumps.
The resulting glue can then be poured off into suitable containers and used immediately. It will have a shelf life of about two weeks but this will depend on the ambient temperature where you are. You can keep the glue in the fridge. Once it goes off it needs to be thrown away so the best idea is just to make enough for a weeks work and make fresh the following week.
…and below is the excerpt from Cennino Cennini’s book
Cennino Cennini – How you Make Batter or Flour Paste
To begin with we have to make . . ., that is; and they are known as various sorts of size. There is one size which is made of cooked batter, and it is good for parchment workers and masters who make books; and it is good for pasting parchments together, and also for fastening tin to parchment. We sometimes need it for pasting up parchments to make stencils. This size is made as follows. Take a pipkin almost full of clear water; get it quite hot. When it is about to boil, take some well-sifted flour; put it into the pipkin little by little, stirring constantly with a stick or a spoon. Let it boil, and do not get it too thick. Take it out; put it into a porringer. If you want to keep it from going bad, put in some salt; and so use it when you need it. [p. 65]