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!
Is there a shelf life for gesso?
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:
- A steel or glass bowl
- Gilders whiting
- Pre-made Rabbit Skin Glue
- A fork
- Old tights or a tightly woven sieve
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.
What is Gesso?
Gesso is an essential art supply that is widely used by painters to make their canvas ready for painting. Acrylic gesso serves to protect raw canvas from the deteriorating effects of oil paints while also providing a smooth and resilient surface for oils and acrylics to perform at their best. Although most acrylic gesso is similar to white acrylic paint in consistency and opacity, it comes in a wide range of thicknesses and opacities.
Although gesso is traditionally white, it is now also available in black, clear gesso, and colored gesso.
You can also dye your gesso to achieve any desired color. Simply add a few drops of acrylic paint to the gesso and you’ve got colored gesso.
The consistency and texture of gesso vary based on the brand. Some are thinner and more viscous liquid, while others are thicker. Some go on more smoothly, while others leave a textured finish. You’ll have to try a few different brands to figure out which one you prefer.
Why does Gesso go Bad?
If you don’t store gesso in a proper manner then it can cause growing bacteria or mold. When you don’t close the lid properly and oxygen gets in, it will dry out. If you mix up a cup of gesso to use and dump the leftover into the jar and use the tap water to clean the brush, it can mess up the gesso. Just close the lid or keep the gesso in an air-tight container after use. When you won’t use the gesso for years it may develop a foul smell and you can see mold growth then it might have gone bad.
Can Gesso Grow Mold?
Gesso can encourage the growth of mold and bacteria. Contamination is the main reason you’ll notice mold growing in gesso. Water exposure or wet brushes dipped into the container are the most common causes. Even the tiniest bacteria that may have been present in the water is quickly absorbed by the gesso.
Bacteria can quickly become an issue, which is exacerbated when the container is kept in a warm environment. Bacteria thrive in moist, warm environments, so it’s critical to avoid cross-contamination.
To avoid contamination avoid putting leftover gesso into the main container. Always dispose of it after use. Don’t put any paintbrushes or other art tools into the container.
How Long Does Gesso Paint Last?
Gesso does not go bad until you store it poorly. The life of gesso depends on how you use it. A container of gesso can last for a few years if you take care of it properly.
When you’ve had a gesso container for a long time, you’ll notice that the acrylic medium and gesso paint have separated. Because the gesso is much heavier than the medium, they will easily separate if left unsupervised for a long time.
If your gesso has separated, it doesn’t necessarily mean it’s bad and should be discarded. It’s as simple as mixing it back together and it’ll be ready to use again. You must take precautions to ensure that your gesso lasts for an extended period.
