Firstly, however, she emphasised the OH&S aspects of this crazy, unpredictable and exciting way of firing. You must wear covered in shoes long sleeves and long pants preferably of non synthetic material. After glazing must make sure you have thoroughly cleaned glaze off the bottom of the pots. Only allocated people firing should be near the kiln. When it is time to take your hot pot out you should have worked out the most direct route from the kiln to your reduction bin such that you do not cross someone else's path. Of course, you need to wear long leather gloves and use tongs.
Marienne and Dean Mc Coll had made up a variety of glazes prior to the Raku Day. It is good to glaze a day before but we dried our pots on the day by placing them in a box with a fan heater on low blowing into it. The glazes included, lemon lustre, white crackle, blue, plum, coppers. The recipes for these glazes are in a folder in our library.
Marienne 's advice is:-
It is all too easy to simply dip your pot in a bucket of glaze and hope for the best. Much better to work out your glaze plan before you arrive, while there are no distractions. Put as much thought into glazing as you did in making the piece and you won't be disappointed. Record what you have done.
Marienne showed us some techniques for decorating:-
1.Masking tape or sticky labels and cutting out shapes with a Stanley knife and sticking the shapes onto your pot then glazing. You remove the tape before firing. Where the shapes were it is not glazed and is
left black after reduction.
2. a slip trailer filled with craft glue can make marks on pots prior to glazing.
3. String tied around pots before glazing can make marks.
4. Wax resist, Marienne likes to use Vaseline mixed with a little turps for this because it doesn't run and it dries quickly.
5. Permanent pens can act as a resist, crayons too but they are more problematic.
We used a kiln that sat on a brick base with a hole facing the gas bottle for the gas burner to be placed. It is important that air is allowed around the burner. You do not stick it right into the kiln. A piece of shelf was placed at the back of the kiln so that when the flame hit it, it bounced off sending the flame around the kiln. The flames should not be directed at the props holding the shelf up. As Marienne pointed out, there was plenty of room vertically in the kiln so tall shapes could be fired more economically than little pots. Marienne placed a short stainless steel cylinder on the top opening of the kiln to act as a chimney to help draw the air through.
Firstly, make sure the regulator is threaded into the gas bottle properly (not cross threaded) with no gas escaping. Once you turn the gas on at the bottle you then operate the pressure from the regulator.. Use paper or a long match to light the burner facing into the kiln. The first firing usually takes longer than subsequent firings when the kiln is already hot. It took us one hour. In that time the regulator was slowly moved from 1 Psi to 4 psi no more.
When the kiln has reached 1000 degrees centigrade hold it at that temperature for 3 to 4 minutes to even out the bubbles in the glaze. When lifting the kiln up remember to keep it straight so as not to let the fibre touch the pots.
Sometimes the burner will make splutter noises if it has air or moisture in it. Clear it by turning the flame up to high for a few seconds facing away from the kiln making sure it is safe to do so.
If you brush detergent mixed with a little water over connections of the burner to the cylinder and it bubbles this indicates the gas is leaking.
When changing over to another gas bottle you must first turn the knob on the bottle off.
Reduction in tins
I place a handful of sawdust in the reduction bin but because I don’t want the sawdust to touch my pot in case it pits the glaze, I sit my pot on a piece of shelf to raise it up a little then put in lots of shredded paper around the bin., I find shavings are better than really fine sawdust ,which should only be used when wearing a mask. Then place a tight fitting lid on top .When burping the bin as soon as you lift the lid the paper will light and flame up. You then throw a handful of sawdust on the pot and put the lid back on. Great care needs to be taken doing this. Pots need a minimum of 15 minutes reducing before opening the tin.
Marienne says she doesn't use shredded newspaper as she is not sure if the burnt ink gives off toxins. However, she does use other shredded paper. You should wear a mask if you use fine sawdust . Never place used reduction materials in the plastic Otto bins where they could reignite and start a fire in the bins.
Reduction in the kiln
Marienne showed us, alternatively, how to reduce in the kiln. At 1000 degrees centigrade, open the kiln to cool it quickly to about 730 or 750 degrees by looking at the pyrometer inserted in the hole on the side of the kiln. Then close all gaps in the kiln with fibre and leave the burner on low so that you soak the kiln for 5 minutes. Now you are reducing by starving the kiln of the oxygen.
Check out references in our library for Raku.
Report by Ingrid Tristram edited by Marienne Stollery