Glaze colour tests

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Online video "How Glazes Work" course student £80.00 now.
Membership expires after 1 Year.

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Linda Bloomfield’s online video glaze course: “How Glazes Work”

Do you want to learn about glaze chemistry but don’t have the time to spend weeks on a course?

I’ve carefully constructed, edited and condensed quite a lot of content into a short glaze course. By the time you finish, you will have a good understanding of the principles of making a glaze and, knowing what each ingredient does, you will have some confidence when it comes to adjusting your glazes. You will also have gone through some key practical steps in making glazes and will have seen some ‘good practice’ which will ensure you get reliable, repeatable results.

Glaze chemistry

This covers the theoretical elements of the course. You will learn about:

  1. The three main components of a glaze and what each material contributes to the glaze.
  2. The difference between a glaze recipe and molecular formula and how it relates to glaze stability.
  3. Glossy and matt glazes, adjusting glazes and correcting defects.
  4. Adding colour, in the form of oxides and stains. Health and safety.

Practical: How to make a glaze and how to add colour to your glaze.

This is a practical session on how to make your own glaze and add colouring oxides.

Glaze colour tests
Colour tests by Katherine Message

Materials and preparation required: You will need to make 15 test tiles, rectangular clay slabs around 6x4x0.5cm. You will need to fire the test tiles in a kiln. I prefer stoneware temperature 1250°C, cone 8, but you can use higher or lower firing temperatures and choose your own glaze base.

Materials list:

  • 15 biscuit fired test tiles.
  • Glaze materials:
  • Potash feldspar 1kg
  • Quartz 1kg
  • China clay 1kg
  • Whiting 1kg
  • Borax frit 1kg
  • Colouring oxides
    • Copper oxide 100g
    • Chromium oxide 100g
    • Tin oxide 100g
    • Manganese dioxide 100g
    • Rutile 100g


  • Who is the course for? Beginners and intermediate potters will find this course useful, especially if you want to learn how to make your own glazes and understand what each material contributes.
  • Who is teaching the course? Linda Bloomfield trained as a materials scientist and worked at Imperial College in London before having children and becoming a potter. She has written six books on glazes and tableware and teaches workshops on understanding glazes. The online course covers similar content as her weekend workshop.
  • How long does the course take? The theory video takes half an hour to watch and is divided into four sections. The practical session takes half an hour to watch and around two hours to complete the glaze tests yourself.
  • Can I take the course at any time? You can watch the videos and complete the practical any time up to one year from joining.
  • How do I ask questions? You can ask questions in the comments at the bottom of the course page.
  • How much does it cost? £80 for a year’s access


Thank you, it’s a very good informative course and very interesting to learn about some of the science behind glazes. Catherine

Firstly, your voice is so calming and relaxing that I can listen to the course over and over. I thought the content was very rich and informative. What is great about it that one can go back and listen again and again to understand everything well. I really enjoyed the video, it was very well shot and edited and just long enough for one segment. I also think that the price is very generous for all the information people are getting. Adamina

I would like to thank you again for a brilliant course. It helped me to understand the concept of glaze chemistry on a different level and motivated me endlessly. As I had run out of pots I have spent all week throwing, got sore fingers…can’t wait to apply my new knowledge to my glazes and experiment & develop a yellow of my own.
Thanks to feeling so happy & confident after your course I started the instagram and how lucky …now I can read your posts every day…awesome. Susanne