The color? Good. The liner glaze? Safer. The crazing? Weakens the piece.

Color like this, from commercial brushing glazes, has become so trendy that multiple problems associated with it are being ignored by potters and hobbyists at cone 6. First, crazing (this network of fine cracks): When people use dense-burning bodies, ware doesn't leak, so it is deemed to be OK. When ware is made using stoneware clays having higher porosities, and it leaks, the clay bodies are blamed. And the poor strength resulting from the crazing is also blamed on the clay. However, this potter has done two right things:
1. Using an iron-stained honey glaze on the inside (e.g. GA6-B). It does not, cannot, leach heavy metals. Many are misinterpreting the ASTM D-4236 label on glaze jars and using intense heavy metal colored glazes on food surfaces!
2. The honey glaze inside does not craze so the mug does not leak even though the body has a higher porosity than the supposed vitrification magic number of <0.5%.
The bottom line: Use glazes that don't craze, DIY ones if possible or necessary, don't use really bright colors on food surfaces.

Dec 6: I have been waiting since Dec 1 for someone to notice this was AI-generated! That happened today. I used an AI image for an obvious reason: A real piece would offend the maker. AI produced this on first try as representative of what's on social. Yes, AI photos are less authentic than DIY, so are pieces made in isolation of awareness of the critical design and safety flaws outlined here. This page gives part of the solution and links to full solutions.

Related Pictures

Is this what pottery has come to?

Brightly colored commercial brushing glazes

There is an undeniable appeal to the bright colors of many commercial glazes. While nobody is recommending abandoning them and going all-in on DIY, there is an appeal to having more control. If you are a potter, hobbyist or small manufacturer, consider: Do we want customers eating and drinking from these kinds of glazes? This type of ware is often crazed (runny glazes do that, especially on bodies they were not designed to fit). These are also prime candidates for leaching the high percentages of the heavy metals they contain. All those layers running and pooling on the insides can make pieces into glaze compression time bombs. For food surfaces, the glaze manufacturers want us using their recommended balanced, lightly colored products. Good news! These base recipes are also the easiest to make yourself. When did we get intimidated about mixing our own glazes anyway? No one has to go full mad scientist on DIY here. Research the common ingredients your supplier offers. Use recipes that pass a sanity test. Be a savvy consumer - these colored products are expensive and using them only on the outsides will cut your costs in half. Learn to add pigments to your base recipes and save even more. Then learn to make and use dipping glazes (not dripping glazes) and save time also.

Links

URLs	https://www.astm.org/d4236-94r21.html ASTM D-4236 - Standard Practice for Labeling Art Materials for Chronic Health Hazards - It is not what you think! A standard that "applies exclusively to art materials packaged in sizes intended for individual users of any age or those participating in a small group". It "concerns those chronic health hazards known to be associated with a product or product component(s) when it is present in a physical form, volume, or concentration that in the opinion of a toxicologist has the potential to produce a chronic adverse health effect". The word "toxicity" is not mentioned on the page nor any methods for determining such. Furthermore, the labelling refers to hazards to which the potter is exposed in applying the glaze to the ware, long term, in small hobby quantities. IT DOES NOT ADDRESS leaching hazards the ware presents to users of the pottery. Even then, the standard states that "it is the RESPONSIBILITY OF THE USER ... to establish appropriate safety, health, and environmental practices ... based upon knowledge that exists in the scientific and medical communities". It also admits that "since knowledge about chronic health hazards is incomplete and warnings cannot cover all uses of any product, it is not possible for precautionary labelling to ensure completely safe use of an art product." It is interesting that one manufacturer displays this warning on pages relating to dipping glazes and accessory products (which are used by manufacturers): "Safety Warning: Tableware producers must test all finished ware to establish dinnerware status, due to possible variations in firing temperature and contamination." This warning does not appear on brushing glazes, even the reactive metal-saturated ones that potters and hobbyists use!
Glossary	Commercial hobby brushing glazes These are an incredible benefit to pottery beginners and pure hobbyists. But they can also be an obstacle to progress and affordability as your skills improve.

URLs

https://www.astm.org/d4236-94r21.html
ASTM D-4236 - Standard Practice for Labeling Art Materials for Chronic Health Hazards - It is not what you think!
A standard that "applies exclusively to art materials packaged in sizes intended for individual users of any age or those participating in a small group". It "concerns those chronic health hazards known to be associated with a product or product component(s) when it is present in a physical form, volume, or concentration that in the opinion of a toxicologist has the potential to produce a chronic adverse health effect". The word "toxicity" is not mentioned on the page nor any methods for determining such. Furthermore, the labelling refers to hazards to which the potter is exposed in applying the glaze to the ware, long term, in small hobby quantities. IT DOES NOT ADDRESS leaching hazards the ware presents to users of the pottery. Even then, the standard states that "it is the RESPONSIBILITY OF THE USER ... to establish appropriate safety, health, and environmental practices ... based upon knowledge that exists in the scientific and medical communities". It also admits that "since knowledge about chronic health hazards is incomplete and warnings cannot cover all uses of any product, it is not possible for precautionary labelling to ensure completely safe use of an art product." It is interesting that one manufacturer displays this warning on pages relating to dipping glazes and accessory products (which are used by manufacturers): "Safety Warning: Tableware producers must test all finished ware to establish dinnerware status, due to possible variations in firing temperature and contamination." This warning does not appear on brushing glazes, even the reactive metal-saturated ones that potters and hobbyists use!

Glossary

Commercial hobby brushing glazes
These are an incredible benefit to pottery beginners and pure hobbyists. But they can also be an obstacle to progress and affordability as your skills improve.

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