Does your studio look this dusty at the end of the day?

Small dust particles (i.e. 1 micron or less) get right into the alveolii in your lungs, clogging them up and causing inflammation, only being expelled very slowly. Also, they can stay suspended in the air in the room for days before settling.

It isn't just silica dust that can mess up your lungs, but any fine dust. And the most damaging particle sizes are too small to see.
So:
- minimise the amount of dust created in your work
- mop or wet wash all surfaces and floors to remove dust
- have an air flow through your studio, with openings for air to flow both in and out
- when doing dusty work, and afterwards, wear a good dust mask - rated P3 and CE marked for European standards. Those disposable paper masks that aren't rated, or any masks rated P1 or P2, are inadequate in a busy studio, and don't save much money, so why use them?
- if you have a beard, shave off at least the outline of the mask, or wear a ventilated hood

The effects of dust accumulate slowly, so precautions now will avoid problems years down the line.

I'm jumping over to arsenic for today's health and safety post, as another potter asked for my opinion on a problem which may be of interest to you all.

Whilst the EU only has leach testing laws for lead and cadmium, France (like Ireland, Netherlands and possibly others) has additional laws on leaching limits. In France, these cover aluminium, cobalt and arsenic, with limits of 1, 0.02 and 0.002mg/kg. The arsenic limit is very low, about a tenth of the value that the EU are discussing for forthcoming EU wide legislation.

Although arsenic used to be used as an opacifier in low fired glazes, it is nasty stuff. It is readily absorbed through the gut, as well as the lungs and skin. Death from acute toxicity takes less than 1g, but a bigger risk is long term exposure to low doses, which causes cancer and also attacks many of the body's functions.

So, this French potter had two pieces tested, and both failed with excess arsenic. But he hadn't used any arsenic in the clay or the glaze, so where could this impurity have come from?

He isn't in an area where arsenic is found naturally, or has been deposited from man's pollution, so it is unlikely to have come in through the water supply.

Although the ores used for the cobalt and copper colourants often include significant quantities of arsenic, most if not all of this should have been removed in the purifying process, and the small proportion of colourants cannot account for all of the arsenic. But we need to remember that copper can markedly increase the leaching of other metals from glazes - not just in lead glazes.

With a bit more research, the clay looked like a likely candidate. Clay can filter arsenic out of water, so if it was dug from an area with high arsenic in the groundwater it would have soaked this up.

So what to try?
- reduce the fluxes and fire hire to reduce leaching
- use a different clay, ideally very different, for example using a ball clay instead of kaolin(and making other tweaks accordingly)
- test with either scientific grade pure copper, or no copper

More later!

Gloves in the Studio

In the workshop it is theoretically only necessary to wear gloves if dealing with a toxic substance that can be absorbed through the skin, which excludes most potter's materials. But if you have cuts or other breaks in the skin you should wear gloves if dealing with any toxic materials, and also it makes it less likely that you will ingest any materials by taking material on your unwashed hands to your mouth.

There are many materials available, but nitrile is generally proof against most things in the studio. Avoid latex as you may develop an allergy to it, and I can tell you that going into anaphylactic shock is not pleasant and will disrupt your plans for the next couple of days. Gloves can be disposable or reusable - I would recommend reusable, washing them before taking them off.

Lead Leaching in Glazes for Tableware

I was going to address this later, but the EU's work on new regulations has just clicked forward another step, and needs discussing.

The EU have done good research on the leaching of lead and other chemicals (e.g. Barium) from glazes. This was prompted by the realisation that if people ate and drank everything from tableware that complied with the current leaching tests, their daily lead intake would be way over the daily maximum set by the European Food Safety Agency.
Now they have asked for feedback (until 26th June 2019), and the aim is to have the directive adopted early in 2020. From there, it is likely that the standard will be adopted globally as an ISO standard.

The approach they are taking is sensible: to have a much lower threshold that is likely to effectively stop lead glazes being used on the inside of everyday tableware, but then to have a more lenient standard on articles marked for occasional use. Items can be marked to say whether for everyday, occasional or non food use, and potters/manufacturers can self certify, so no mandatory use of test labs.

For more into, go to the link below, click on the download button at the bottom, then read that document and those it links to. And then give your feedback!

https://ec.europa.eu/info/law/better-regulation/initiatives/ares-2019-325847_en

For those Brexiteers who envisage Britain floating through space unencumbered by EU regulations like this, it is likely that the UK will adopt them regardless. Why? This has little to do with the health of the population, and more with economics. If we don't adopt them, we won't be able to export non-compliant items, and we will also open the gates to low cost, poorly made items from outside of the EU, which together will probably kill our industry.

And after my previously saying that lead hazards in the studio are over rated, why am I so concerned about lead in tableware glazes? Basically because the lead is not tightly bound in to the glaze, which is exposed to a more corrosive environment, and is then more easily absorbed by the body. Also, you may be prepared to risk lead poisoning, but you don't have the right to poison your customers.

Microwave safe?

Obviously not!

I was cooking some poppadoms in the microwave - brush each side with a little oil and put them in the microwave for about 45 seconds with a piece of kitchen towel on top.

On doing the 3rd one, this happened. It looks like the centre of the plate sheared off horizontally, and then a couple of cracks propagated to take the wedge out. I think the cause is that the centre of the plate got a lot hotter than the rim, so the centre was trying to expand and the rim wouldn't let it. As a result, the centre sheared horizontally into two main pieces, from the top and bottom surfaces, and when that happened the cracks propagated to the rim, all in all resolving the pressures that had been building up.

It may have been exacerbated by this being one of the newer style microwaves, with no rotating turntable, so the microwave pattern doesn't vary over the plate, allowing hot spots to build up more.

In hindsight, when taking out the previous poppadom I noticed that the rim of the plate was quite warm, but didn't think anything of it.

So should having a curry and making some poppadoms be part of your testing procedures for tableware?

Even without the poppadoms, it may be worth putting a little oil onto a plate and heating it in the microwave - unlike water, the oil won't evaporate, so higher temperatures can be achieved.

For further information on making microwave safe pots, have a look at the Microwave Safety page - to access the page, either log in or register (there's no charge)

Respirator

Dust, and in particular crystalline silica, is probably the major health hazard for potters. Good studio practice should keep dust levels low, but when doing any activity that may create dust a respirator should be worn - and also kept on for a few hours afterwards, as it cantake a long time for the smallest particles to settle.

You should only use a type approved respirator, with the highest level of protection - EN149 FFP3 in the EU or N100 in the USA. Surgical masks, pollen masks, non-certified dust masks and the like won't protect you.

Reusable respirators work out more cost effective than disposable ones, and tend to fit a wider variety of face sizes, though disposable masks are useful for students on courses and other occasioanl users.

The respirator must be a good fit, and you may need to try a number of models and sizes until you find one that fits your face properly. It's worth considering getting a fit test kit to check this - they don't cost much. Also, note that any facial hair under the sealing rim means you need to reach for the razor, or go for a full face mask.

Look after your respirator - keep it in a sealed bag when not in use to keep dust off, maintain the straps, and replace the filters when needed. Your health depends on it!

And, in case you're wondering, this spec of respirator will help protect you from coronavirus, though you should use a disposable respirator, and also ensure that there is no cross-contamination when putting it on or taking it off.It will also protect you from the smoke from bush fires - the smoke particles are a major health hazard.

For further information on respirators, have a look at the studio and firing respirator pages - to access the page, either log in or register (there's no charge)

Molybdenum

Molybdenum trioxide is used by those researching the far side of crystalline glazes, and it can also be used as a colourant.

It is a pretty benign material, and can be used quite happily on food contact surfaces. Ingesting high doses can cause weight loss and affect muscles, but this is far higher than you will encounter in a studio. On inhalation it may cause some inflammation of the respiratory tract, but the evidence isn't clear and again the concentration is high. There is also some indication that prolonged exposure may cause lung cancer, but again this isn't clear cut.

There are really two areas of concern. First, it is slightly soluble in water, and forms an acidic solution which can be an irritant to the eye (though no lasting damage). Secondly, in forming crystals it vaporises in the kiln and then condenses on the glaze surface, and inhaling a lot of the kiln fumes could be harmful. You don't want a kiln vent that pumps air through the kiln, as that will get rid of the molybdenum, but a well ventilated kiln room or a vent hood over the kiln would be good practice.

For further information on respirators, have a look at the Molybdenum Trioxide and Molybdenum leaching pages - to access the pages, either log in or register (there's no charge)

Chromium (VI)

Whilst trivalent chromium is a pretty innocuous way of creating green glazes, using hexavalent chromium to create yellows and oranges is a different kettle of fish.

All the hexavalent chromium compounds are highly toxic. Potassium dichromate is, I believe, the only one that has been used in ceramics, though trivalent chrome oxide can sometimes create a yellow/orange glaze, which is also almost definitely a hexavalent chromium.

Things it can do are:
- it is caustic on the skin as a solid or solution, and can damage the eyes or blind you
- it is highly corrosive to the respiratory tract
- exposure to the skin or respiratory tract can initiate an allergic reaction (causing asthma in the respiratory tract). Once started, this can be triggered by small levels of chrome exposure
- it is also highly corrosive to the digestive system.
- It is a carcinogen, and also causes inheritable genetic damage
- about 50% of the amount inhaled, and 7% of that ingested, enters the body. It then causes damage to the liver, kidneys and cardio-vascular system
- It decomposes at about 500°C, but then the potassium chromate boils at 1000°C and is just as toxic, so kiln fumes may be an issue

If a yellow or orange chromium glaze leaches, this is not great news for the user. Thus don't use these glazes in any area that may come into contact with food or drink.

Thankfully since 2017 the use of this substance has become tightly controlled in Europe under the REACH regulations, but if you live elsewhere or still have some in your workshop, please exert due caution! At all times wear gloves, goggles, dust mask and an apron or other protective clothing. Or, better still, have it properly disposed of as hazardous waste (don't pour it down the sink as it is highly toxic to aquatic life).

For further information on Chromium (VI), have a look at the Potassium Dichromate and Chromium leaching pages - to access the pages, either log in or register (there's no charge)

Hazards, Risks, Labals and SDS

We've all seen some of these symbols on materials that we use, on the label and the safety data sheet (SDS). These, and most of the format and phrases used, have been standardised in the GHS, a framework created by the UN and adopted by most countries.

Your attitude may be to blithely ignore them, or to reach for every bit of protective kit you have. But, to put them into context, you need to understand the difference between hazards and risks.

The provided information relates to the hazards of the material - that is, unlimited exposure to the material for every day of the year. The user is then meant to assess their level of exposure to the material to determine their level of risk, and base precautions based on that. For example, the risk to a person in a plant processing mined cobalt that has minimal health and safety practice will be much higher than a weekend potter usinga tiny amount of cobalt in their glaze.

So, don't ignore the warnings or get paranoid about them, but use them to think about your level of exposure and risk.

For further information on this, have a look at the Chemical Risks pages - to access the pages, either log in or register (there's no charge)

Chromium (III)

Here we'll look at the trivalent form of chromium, which appears as the green chrome oxide (Cr₂O₃) - in a follow-up post we'll look at the hexavalent form. An easy way to differentiate them are that trivalent chromium is green, whereas hexavalent chromium is generally orange. A later post will look at Cr (VI).

Chrome oxide has little toxic effect on humans - the main risk is that an allergy against skin contact can be developed. Though the risk is low, it would be a real pain for this to develop, so it suggests that a dust mask should be worn when mixing glazes, and gloves when mixing or applying chromium glazes.

Chromium can also leach out of glazes, and there are reports of quite high level of 1mg/litre. There is little information available on the valency of the chrome, but the available papers suggest that it is the Cr(III) ion, precipitating out as the hydroxide Cr(OH)₃. This suggests that there is little risk to the user from chromium glazes.

A bigger risk is in disposal of chromium, as the trivalent form is toxic to aquatic life. So it shouldn't just be poured down the drain. Instead, fill a reject pot with waste glaze and high fire it to encapsulate the chromium before throwing it away.

For further information on this, have a look at the Chrome Oxide and Chromium leaching pages - to access the pages, either log in or register (there's no charge)

Coronavirus

Well, although this has been covered to death in the press, hopefully you'll find something in this post useful for you as a potter.

The key thing is that this is a serious disease. At present, 2 people are dying from it every minute in Italy; this would correspond to over 16 every minute in the USA; and here in the UK our death rates are matching Italy's, only we are 2 weeks behind.

Secondly, as there is no cure, the only way to control it is to stop social contact, so it can't be passed between people. Unrestricted, each person would typically infect 3 others, about twice as infectious as 'flu.

The key factor is stopping its spread, rather than worrying about whether you or another individual will survive.

In the most infected parts of Italy, the medical system has gone into meltdown, so many cases of the virus cannot be treated due to a lack of beds and ventilators, and also many other health issues cannot be treated.

Here in the UK, current NHS guidelines are that you will not get a ventilator if you are over 65, or if you have problems with 2 organs or more, as your chances of survival are deemed to be to low - and that's with only 50 deaths a day.

How it will pan out in the USA and other countries where they don't have state provided health care for all, I am not looking forward to finding out
The virus can stay airborne for 3 hours after somebody has exhaled it. If you have an N95 or higher (US) or P2/P3 (EU) respirator, then it will reduce your risk of infection. But pay attention to the life of the respirator, especially if disposable.

It will live on hard, dry surfaces for up to 3 days, less on absorbent surfaces, but longer on cold, damp surfaces like wet clay. Clean with at least 65% alcohol, or 0.5% hydrogen peroxide bleach, or 0.1% sodium hypochlorite bleach

Also,
- do not attend or give any more pottery classes
- do not run or participate any communal firing activities
- do not attend or exhibit at any exhibitions or shows
- if an outlet has your work, consider whether it is morally acceptable for you to encourage it to stay open by showing your work

For further information on this, have a look at the Coronavirus COV-19 page - to access the page, either log in or register (there's no charge)