Rabbit skin glue (rsg) comes in a granular form. Because of its organic nature, it needs to be stored somewhere dry where it can be safely kept for many years.
To use it however, it needs to be made into a liquid solution.
Rsg is used in gilding in almost all the different stages. First, it is used as an initial size (first coat) for the surfaces to be gilded.
This is followed with it being added as a constituent of gesso and finally of bole. Traditionally, it is also used in the ‘gilders water’ which is used in the final
application of leaf - however, these days, the cleaner gelatine is usually used instead. Each of these areas also use the rsg at different strengths.
This section is used to create a ‘10-1’ solution. This is the 'base strength' from which all other recipes can be developed from.
For this exercise, you will need the following equipment:
A pint glass, or similar container
Rabbit skin glue crystals
A small container for measuring
To begin with you will need to soak 1 part of rabbit skin glue granules into 10 parts of cold water and leave for at least two hours, but preferably overnight.
The granules are rsg that has been dehydrated. Although they come in many forms, they are all prepared the same way.
The granules you see here, are the most common form.
It is easy to make too much rsg at first, as it is hard to determine how much you will use, but it is always wiser to make more than you need.
To measure the amount of granules and water, I usually use a small plastic 'cocktail shot-glass' for the smaller gilding jobs. One of these filled with granules
will eventually make about a third of a pint of glue (150ml), or 3 pots will make a pint (450ml).
The following morning (or after a couple of hours, if you're in a rush) you will have found that the rsg has absorbed all the water and turned into a thick gelatinous lump.
The mixture will now need to be gently reheated. This can be done with a double boiler. If you don't have a double boiler, one can very easily be fashioned using
a clean tin, small bowl or a smaller saucepan that will sit inside a larger saucepan containing water. Just ensure the can or bowl is not in contact with the bottom of the pan. Ceramic discs are inserted into the bottom
to prevent this, or if not available a couple of spoons on the bottom will suffice. But it's not ideal.
Another way to reheat it (a method I use) is to insert the container (I find a pint glass is the very best) into a large saucepan filled with boiling water and
leave for a few minutes. Replace the saucepan water if it becomes too cool, with another round of boiling water. This way is a lot less agressive, but may take a little longer.
Slowly heat the mixture until all the jelly is dissolved. You will need to keep stirring at regular intervals in order to do this
Although the mixture will become quite hot, it is very important that it MUST NOT BOIL.
Boiling the glue, will introduce air bubbles to the mix and affect its overall properties. This is why it is also not microwaved.
It does not take long for it to dissolve with gentle stirring. Eventually, you will be left with a light creamy coloured mixture.
Using an old pair of tights to eliminate contaminants and lumps, drain the liquid into a clean storage container.
Allow to set naturally on the side.
Once set you will be left with a jelly like substance. If you lightly pull on the top, it should split easily.
When it is needed to be used, just reheat the needed amount in the double boiler (or other method!). It melts at quite a low temperature.
The ideal temperature for using the glue is around 60℃. If it goes higher than 70℃ the glue starts to break down and lose it's strength. If it is too cool,
it will be thicker, coagulated and unable to be absorbed.
Due to its nature, RSG will eventually break down and rot, especially in warm weather.
However, RSG glue can be kept quite safely in a refrigerator, for up to 10 days.
If you forget to put it away, it will go mouldy quite quickly and it can throw of quite a stink! I went away for a couple of weeks once and forgot about the rsg in the studio.
I cannot begin to tell you of the horror that assailed my nostrils when I returned! Please, for the love of your nose, don't do it!