The foundation of all water gilding is 'gesso' (pronounced 'jesso'). Gesso is used to provide a thick hard coating onto the surface to be water-gilded.
It fills in the small grain of the wood, and can be sanded down to an incredibly smooth finish.
As well as a foundation for water-gilding, gesso can also be used as a finish in its own right.
Gesso is a mixture of rabbit skin glue and gilders whiting (very refined and finely crushed chalk).
The following recipe is how to make gesso.
For this exercise, you will need the following equipment:
Reheat an appropriate amount of Rabbit Skin Glue (rsg), previously made up in a 10:1 mix, in a double boiler - ensuring of course that it does not reach boiling point.
Once it has melted, lightly tap the bottom of the container to remove any air bubbles. The temperature should be very warm - imagine a cup of tea after 10 minutes.
Gently pour the mixture into a container in which you wish to make the gesso. This can be any container really, but a steel or glass bowl works very well and is easier
to clean afterwards.
Prepare a suitable amount of 'gilders whiting' to add to the rsg. You can do this by sieving it into a separate bowl, ready to add. You don't necessarily have to sieve it,
as it will arrive in a clean and lump free condition, but if it's been around and used several times, some debris or residue may have gotten into the bag.
Gently add Gilders Whiting to the rsg mixture. This is done by taking the whiting from the container, and lightly sprinkle it into the mixture with your fingers.
Do this slowly and wait for all the whiting to drop to the floor of the glue. At no point should you stir the mixture. Occasionally you can gently tap the
bottom of the bowl to ensure even settlement of the whiting mix and to eliminate air bubbles, but don't stir!
Keep going until it starts to peak through the surface of the RSG, which I'm pointing at in the picture. Once you have reached this point, keep adding more whiting,
but only into the areas where there is pools of rsg, until all the liquid has been soaked up. You don't want to peak the whiting up , although you will get some of this.
You want to find a perfect equilibrium between the whiting and rsg. No liquid left, and no peaks of dry whiting.
Although the amount of whiting will vary, it should be approximately the same volume as the glue-size used.
Once you have soaked up the liquid, your gesso should look like the picture here. Leave this to settle for about ten minutes allowing the air bubbles to escape
all the while gently tapping the bottom of the canister. Once the whiting has completely settled and air bubbles are eliminated as much as possible, you can
gently stir the mixture until an even mix is achieved, although you should again be careful at this point not to introduce any air bubbles into the mixture!
I stir the mix with a fork, as it allows the mixture to flow through the tines, and any lumps can be caught and gently squashed on the side of the bowl.
Eventually, the mixture should feel thick and creamy and have hardly any lumps in it.
Now you have a bowl of creamy gesso. The gesso should now be strained through a pair of tights or a sieve to remove lumps at this point. I buy industrial amounts
of tights for this purpose, and get the strangest looks, but hey ho. All for the art. Gently strain the mixture through the tights. It will catch any lumps and
problem areas, allowing the really pure gesso to flow through.
Once again, you can leave the mixture to help further eradicate any air bubbles still in the mixture, although it can be used from this point on if needed.
When left for some time, the mixture will set into a jelly like substance and just like the rsg, gesso has a shelf life of about one week and will need to
be stored in the fridge.
Before using gesso after it has set, it will need to be gradually brought back into a liquid state by gently re-heating in a double boiler.
When applying layers of gesso to the surface, care should be taken that the gesso remains in a very warm liquid state, as the gesso won't bond if it is too cold.
You should also add just a few drops of water to the mixture between coats, as this will ensure each layer is slightly weaker and prevents cracking and this will
counteract that a small amount of water is also naturally lost due to evaporation.