Ariane Coissieux's technical corner

What an exciting, joyful adventure it is to use waste to make light appear...

 

A process that brings me even closer to the alchemists of the past. 

 

I'm currently working on new glazes, using wood ashes.

 

For many years now, I've been keeping the ashes from the wood-burning stove in my house.

 

I burn beech and oak, as well as anything else that can be converted into heat 🔥 

The ash I get (while heating my house) is very rich and interesting because of the compositional diversity.   For example, for my never-ending quest for blue...

 

 

This goes completely against the guidelines of the great Masters and purists (including my Dad!).

 

Their approach consists of using very pure ashes, obtained from the burning of a single plant. This makes it possible to work as closely as possible with the ash compositions found in their books.

 

Burning plants in a barrel to obtain ash, without taking advantage of the heating effect, is a practice from another era....

What ashes do you have available?

 

Why is a ceramic vessel “food-safe” or not? As a professional producing tableware, it's my duty to be  irreproachable in this field. 

And even more so when I teach glazing techniques to emerging professionals.

 

Unfortunately, the regulations we have to follow are the same as those in industry, with no adjustment to our small-scale craft studios.

I've always worked conscientiously and scientifically. My vessels are all coated with my self composed glazes, respecting the rules of molecular proportions between the different natural components. Thousands of experiments, I'll tell you about it from time to time.

 

In this way, none of the elements are soluble in food-grade acids and bases. So there is no risk of absorption by the user. 

Some raw materials can be harmful if not used properly. To be simple, all the components must be closely bonded to the silica after firing. You can imagine a large silica netting (like a large fisherman's net). The other elements have to be trapped between the meshes. This ensures that they cannot be released when they are in contact with the acids and bases such as milk, salad dressings, drinks, etc.

  

The molecular proportions of the different oxides must be respected (for those who understand: basic oxides: 1; alumina: 0.05 to 0.5; silica: 2 to 6 for firing above 1260°C). 

 

 

I'll stop there with the technical details, but feel free to ask me your questions.

 

Yet, ceramics vessels containing lead, cadmium, uranium, etc. are sold in France. How is this possible? Because imported products (for instance) don't have to follow the same rules as French craftsmen's ware. That's a fact.

 

And I'm not talking about plastic containers etc ... this paragraph would become a 3-volume book of unnecessary anger!