Friday, August 26, 2011

Enameling basics: Annealling



Fired 12-20 times
One of the difficulties with enameling is that sometimes - when you don't follow best practice - everything works fine. Countless times students say - "but I did this before and it worked fine".  If you don't mind sometimes failing, you can be careless - and things might even work out frequently - but if you want to gain control over the outcomes - meticulous attention to detail becomes important. I have found that developing meticulous habits is the only way to reduce your failure rate.
Fired 3-4 times

For the first few years of enamelling I would say that my failure rate was about 25% - that would be typical for a beginner. After 25 years of enamelling my failure rate is less than 5% - but it's still not perfect. That is simply the reality of the world of enameling. The failure rate will, of course, depend on the difficulty of the technique -- but it will always be there. There are literally hundreds of variables and sometimes a few seconds too long in the kiln can ruin a week of work. Enamelling is not for the faint of heart!

Fried to burn-out (usually undesirable)
The good news is that sometimes when things go wrong the results are quite beautiful! However learning to diagnose what has gone wrong will enable you to reproduce those beautiful results. If you want to make a living as an enamelist this becomes important.


So I am going to do a series of  blogs on the basics of enameling. Enameling is an art that requires meticulous attention at every level. The more care that is taken in the initial steps - the less likelihood that unexpected or unwanted results will ensue!

ANNEALLING

The first concern of the enamelist is to prepare the metal. It must be perfectly clean before the necessary molecular bond will be formed.

Different enamelists develop different procedures for cleaning the metal depending on what techniques they use - I will outline a standard procedure here.

The first step is annealing. This means heating the metal to around 1500 degrees. This may seem simple - but there a quite a few things that need to be kept in mind. Accuracy in annealing will make all the other stages go more smoothly.

In a perfect world - when you bring the piece out of the kiln it will have a thin layer of grey firescale, which will flake off immediately upon dropping the piece in cold water (quenching) The metal will look light pink and be only slightly mottled.

If the piece has not been heated long enough it will be a dark or yellowish red even after quenching. If it has been heated too long it will have heavy firescale that will take a long time to get off. 

As in many cases in enameling - it is possible to give an accurate diagnoses of the problem after - but not possible to give exact times/temperatures  before the fact. Success comes only with practice.

As you place the piece in the kiln there are a few things that will give you clues as to when the piece is ready. 

First the tray will start to glow the same colour as the kiln and then the piece will,  but you want to get the piece out just before that. There is a fairly small window ( a few seconds) when this happens and the piece is perfectly ready.  Once you take the piece out of the kiln it will look different. The tray will no longer appear to be glowing, but the piece should be glowing a dull cherry red. This will only be noticable once the piece has come out. Inside the kiln it will look greyish. These observations are VERY subjective. There is no substitute for making your own observations.


This does not accurately represent what the eye sees - but shows how subtle the changes are over a few second breaks

Careful attention to kiln temperature and time at the annealing stage will give you a benchmark time for firing later.

After quenching the piece should only he held LIGHTLY by the edges, or by the underside (the side you are not working on.


A short time in a COLD pickle of Sparex #2, citric acid or vinegar and salt. Enamel should not be put in a hot pickle as this may cause deterioration of the enamel.


After the piece looks completely pink, remove it by the edges and neutralise it with a bit of baking soda. If the firescale doesn't come off with a LIGHT brushing it needs to go back in the pickle.


Now you are ready to apply enamel!

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