Using Raw Materials

Hot Clay’s raw materials have been carefully selected with ethical, health and safety and environmental considerations. We have limited the range to keep it simple although we plan to expand in future. You are welcome to give us feedback and we will listen to preferred materials or amounts. We are focused to our customer’s needs, but we do apologise if we don’t have quite what you want, in the size wanted.

 

Ethical

 We have sourced all the materials from the UK. Many originate from Europe, with some from America and Australia. We have avoided countries that have less ethical standards and have been conscious where we can of sourcing locally, to minimize our carbon footprint.

 

Health and Safety 

  We are mindful of the risks and hazards associated with raw materials. We have kept the labelling as simple as possible. As with all materials in ceramics they are accompanied by an SDS, a safety data sheet. We have remained true to the supplier’s information, although when recommending PPE (personal protective equipment) we have been more cautious and advised in most cases a full kit to be worn. In general, and to be safe, we recommend treating all raw materials as hazardous even when not. It is a good habit to get into and it will cover any future advancements either in regulation or knowledge.

We strongly advise that raw materials should not be used by children or vulnerable groups. Do not use in kitchens or domestic areas, and practice good hygiene after use. If you have questions or seek further advice don’t hesitate to ask.

 

Environment 

We do ask that you dispose of the residue and leftovers responsibly. Sedimentation tanks are a useful addition to the studio, not only will they prevent the blockage of sinks and drains but they will prevent unnecessary materials/contaminants going into the water system. When the tank is full, pour off the clear water and dry the remaining contents. A hot summers day is perfect for this. Then contain the dried contents and take to a recycling centre to be disposed of correctly.

You may have been inspired to use materials after seeing a recipe or social media post of a wonderful glaze. But there is much to learn about before buying the ingredients, measuring the quantities and simply adding water.

With each material there is a breakdown of its composition. This is referred to as its analysis. It is done so in %. All materials are made up of many basic ingredients like silica, alumina etc. They can look similar but it’s the % that will make the difference. Although we have given guidance as to the likely content of the % within your purchased raw material, the actual analysis of what you have bought is likely to be a little different. The producers of the material might have measured the analysis in one place, at one point in time. As it originates from a geological deposit, it will vary. This is not a problem for industry, with ceramic technicians on hand to batch test and adjust recipes but for the hobby potter, it can be the cause of major frustration. Wherever possible we have clarified the analysis to advise whether it comes from the supplier or one which is more of an estimate. We also have included particle/mesh sizes and any other details when they become available.

 

If you have put all the ingredients of a glaze together, fired and it is now different to what you have seen, the above reason might be the cause. But there are more common reasons, such as water content, application and firing. This is why ‘testing’ is very important, and to keep testing. Never assume from one purchase to the next it will be the same, as materials can vary bag to bag.

 

It is often suggested that one raw material can be substituted for another but as mentioned before they can be similar but not the same. You will have to adjust the amount you include in your recipe. In this regard it is important to learn basic chemistry, mole % and unity formula, see below.

Further Information 

We recommend going on a course that shows you how to make glazes, they will advise on common misconceptions and various pitfalls. A great beginners’ book is ‘The Ceramic Glaze Handbook’ by Mark Burleson. It is very pictorial and shows in simple ways what each material does in a glaze recipe. John Britt’s YouTube videos are worth watching, so you can learn to look past the name of a material and see it in its composition, he also explains mole% and unity formula.
Linda Bloomfield’s books and videos get into the chemistry of glazes. She explains why and how glazes look the way they do.

Social media pottery evangelists such as Sue McLeod make the complicated simple and Tim Thornton is very scientific.

Digitalfire has a fantastic resource of information on all raw materials, their use and health and safety. It is also a software which can adjust recipes due to shortage of a material, as does Glazy.org but with more pictures.