Creating Saturated Epsom Salt (Flocculant) Solution

Epsom Salt is one of the most popular and widely used ceramic glaze flocculants. This is because of the affordability and accessibility of the product. Epsom Salt is also popularly referred as "Magnesium Sulfate". The salt is initially dissolved in water, resulting in breaking the bond between the magnesium and the sulphate so the magnesium ions are free to attach themselves to the clay particles.

To understand what a saturated epsom salt solution is, we need to understand what a saturated solution is.

What is a Saturated Solution?

A saturated solution is defined as a chemical solution containing the maximum concentration of a solute that gets dissolved in a solvent. Any addition of solute over this will not dissolve in the solvent.

In this scenario:

  • Solute is Epsom salts
  • Solvent is water

So a saturated Epsom salt solution will have the highest possible number of magnesium ions in the desired quantity of water.

Need for Saturated Epsom Salt Solution:

Epsom salt solutions need to be saturated, as an unsaturated solution can result in more amount of water in the glaze than what is required/necessary.

If your glaze is too thin or won’t stay suspended because it has too much water, then flocculating will only hamper the glaze and thereby the glaze results even further. The water is just a medium for carrying the magnesium ions into the glaze. The aim is to maximize ions, minimize water.

Supplies Needed:

  1. A transparent/clear container with lid. A clear container makes it easier to know if there are any undissolved salt particles at the bottom of the solution. The size of the container can vary depending on the requirement of the saturated epsom salt solution.
  2. Distilled Water
  3. Epsom Salt / Magnesium Sulfate
  4. Silicone/Plastic/Wooden Spoon/Stirrer

Instructions to Make:

  1. Fill the container with distilled water (recommended upto 8/10ths of the container capacity, do not fill it up to the brim)
  2. Add a small amount of epsom salt to the distilled water and stir. The salt starts dissolving.
  3. If the salt dissolves in it's entirety and disappear, add more salt and stir. Repeat this step until you have a layer of salt settling at the bottom of the container.
  4. Once you have a layer of salt settled at the bottom of your container, you have a saturated solution.
  5. If you are storing the saturated solution, always check for undissolved salts before flocculating. The salt settled at the bottom can dissolve over time. If there isn't any salt settled, add more epsom salt and stir and repeat the process.

Note: When using the saturated solution to flocculate your glaze, always use the liquid on top and leave the undissolved salt crystals on the bottom.

Frequently Asked Questions:

  • Can I use hot water to create the saturated salt solution?

    Solubility (the ability to dissolve) increases with temperature. Thereby more salt will dissolve overall in the solution (Distilled Water).  When the water temperature is back to room temperature, the solubility will decrease and some of the previously dissolved salts will precipitate out of solution i.e. become crystals again. This can hamper with the glaze and is usually not recommended. Distilled Water at room temperature is ideal.
  • What are the exact measurements for the recipe?

    We have not mentioned exact measurements for the recipe as the magnesium concentration in epsom salt can vary slightly across vendors and batch-wise. Just follow the above steps and you are good to go.

Hope this helps in creating a perfectly saturated epsom salt (Flocculant) solution for your glaze. Please do comment your results and views below. 

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