Deadly materials

As well as teaching at the University for the Creative Arts, I also teach evening classes twice a week at 318 Ceramics in Farnham. 

The classes are mixed ability, 'Exploring Clay' class and a throwing class. 

A few weeks ago, one of my students in the Exploring Clay class came to me to ask for help with a project she was working on. She was carving house numbers into clay slabs for her family and wanted to fill the carved number area with glass. 

The glass was to be recycled from something and the student made several test pieces with her glass and put them into the kiln to see what would come out.

The following week, she had her test pieces out of the kiln and they were surprising..

The glass had melted and formed orange blobs. I asked her what colour the glass was and she produced a jar of broken red glass. 

I was a little perplexed about how the red glass could have possibly changed into such an intense orange colour and we were scratching our heads for a while until I remembered where I had seen that orange colour before...

That intense orange colour was identical to uranium glazes I've seen before in some of my pottery textbooks. It's no longer used as it's obviously a health hazard due to it being radioactive, but there are people who collect uranium glazed pieces (see below)

That still didn't explain the red glass.. so I did some googling and quickly I found out that in Victorian times, uranium was used to create a blood red glass. I asked my student where she had obtained the glass from and she said it was in a jar in the shed of her late mother-in-law, who was a potter, but was nearly 100 years old when she died.

You can see in this photo how intensely red the glass was. 

Unfortunately for my student she hadn't been wearing any protective equipment when smashing up the glass and this just goes to show that you need to know the provenance of your materials because in days gone by they used some very nasty materials that aren't allowed any more.