My kiln has 3 shelves. you can see on the left, there is only one, gas inlet area, at the bottom of the kiln.
Some Kiln shelving has been put on the side, so the gas fire goes up and around.
Turn the gas burner on to KPA5.
We put the bung in at the front of kiln, when temp reaches 500. (1hour)
Turn up to KPA10. It takes a while for the temp to go to 900. (2 hour +).
Start reduction. Turn up gas to 15kpa, start to close off chimney. ( I have a piece of kiln shelf that can be pushed across), black fire will flow high up chimney, let it settle, So only do a little at a time.
You can not close the chimney completely. You will end up with black pottery if you do.
When you reach your temp we do 1280.put every thing back and turn down to 10KPA and let sit (soak) for two hours before turning off.
I did not do it, my husband opened it after turning the gas off, he wanted to see inside. All he seen was red hot. Only opened kiln up about 6 inches. Results were not good the top shelf was pieces of clay every where. All my pottery I had done was broken or had pieces of pottery embedded in them, You could say the pottery had a smashing time.
Do not open your kiln until it cool down.
What is perfect combustion?
Perfect combustion exists when one carbon atom is combined with two atoms of oxygen to form one carbon dioxide molecule, plus heat. But when you are firing a kiln to achieve a certain consistent atmosphere, it becomes a little more complicated.
To achieve complete combustion, the exact proportions of fuel and oxygen are required with nothing remaining. In a gas kiln firing, this is often difficult to attain because of the many variables in fuel and oxygen (which is derived from the air) and the equipment used to mix the two.
The most common fuels used today are natural gas and propane. These are hydrocarbons and when they are properly mixed and ignited, they produce heat, carbon dioxide and water vapor.
Air is a combination of approximately 75% nitrogen and 25% oxygen by weight. Unlike oxygen, the nitrogen does not react (combust) but it still absorbs a portion of the heat and therefore creates a cooler flame.
During the firing of a gas kiln there are a trio of atmospheres that have to be controlled to achieve both a rise in temperature and the desired glaze results. The first, and most important, atmosphere is neutral. It is only in a neutral atmosphere that perfect combustion can be attained. A neutral atmosphere is the most fuel-efficient firing possible.
If the amount of air is increased, or the amount of fuel is decreased, from a neutral firing, the mixture becomes fuel-lean and the flame is shorter and clearer. The gas kiln has now entered an oxidizing atmosphere and the rate of temperature rise will decrease.
If the fuel supply is increased or the air supply is decreased the atmosphere becomes fuel-rich and reduction begins. The flame becomes long and smoky and incomplete combustion occurs. The result is an excess of carbon, which combines with the remaining oxygen and creates carbon monoxide. To convert back to its natural state of carbon dioxide, the carbon takes oxygen from the metal oxides in the glaze, thus altering the finished colour of the glaze. The rate of temperature rise will also diminish under these conditions.
Regardless of the atmosphere necessary for the results you desire for your work, a higher level of efficiency and fuel savings may be attained by firing to a neutral atmosphere whenever possible . With the enormous increases we have seen and will continue to see in fuel costs, it might become highly desirable to buy an oxygen probe and maintain a neutral atmosphere for at least part of your firings.
Oxidation/Reduction- is the result of the colour in your glaze.
Oxidation Atmosphere: A mixture of fuel and air where there is a significant excess of oxygen from the air relative to the fuel; defined (somewhat arbitrarily) as more than 3% excess oxygen.
Neutral Atmosphere: A theoretical mixture of fuel and air where there is a perfect balance between the amount of fuel and the amount of oxygen from air necessary to burn that fuel.
Reduction Atmosphere: A mixture of fuel and air where there is more fuel present than there is oxygen from the air to burn the fuel. For complete combustion to occur in a reducing atmosphere, the fuel must react with all the oxygen from the incoming air and with oxygen from other sources. For a ceramics artist, the important “other” sources of oxygen are oxides of iron and/or copper in the ware being fired, as those oxides are reduced.
When an excess of carbon (fuel) or a shortage of oxygen (air) is introduced, incomplete combustion takes place. Carbon monoxide (as opposed to carbon dioxide) is produced along with heat, though not as much as would be produced during complete combustion. The carbon monoxide then looks for more oxygen, which it takes from oxides in the clay and glaze in the kiln. This is also the reason yellow flames shoot out through spy holes when a kiln is in reduction—the carbon-rich fuel is following the oxygen supply.
Gas Kiln Firing – Defining the Terms
Oxidation Atmosphere: A mixture of fuel and air where there is a significant excess of oxygen from the air relative to the fuel; defined (somewhat arbitrarily) as more than 3% excess oxygen.
Neutral Atmosphere: A theoretical mixture of fuel and air where there is a perfect balance between the amount of fuel and the amount of oxygen from air necessary to burn that fuel.
Reduction Atmosphere: A mixture of fuel and air where there is more fuel present
Firing a gas Kiln.
Cone 10. Glazers.
I glazed all my pots, high firing glazers.
What happens in the kiln is different on each shelf, different at the front, back and middle of each shelf. The temperature is different all over the inside of the kiln.
Firing at high firing gas kiln is a lot of luck. When I get great results from a firing, I end up doing the same glaze in a different part of the kiln.
Using red glazers, at the bottom of the kiln you get red. At the top you get, a beautiful green. That the different between Oxidation and reduction. If only we let the kiln sock longer. We might of got red on top to.
Every firing is different, great fun to open the kiln, and see the results.
In this firing there was only five pieces of pottery.
The kiln shelf before firing .
The pottery plate below.
This plate had stain colours mixed with a base glaze. Some colours burnt out.
I should of put a clear glaze over the top of the colours. To run your fingers over the colours on the plate, it is very rough.
Out side was a blue glaze painted on. the kiln was to hot the glaze burnt off in places.
Great test plate. With what the colours did.
Nice colours over all.
Retile blue. glaze.
The two pictures below is rutile blue glaze , love the different colours this glaze shows.. It is all to do with the different way you apply the glaze. Retile Recipe I use. Where you place your pottery in the kiln, also shows different colours in the glaze.
In the last picture the kiln was to hot on one side, that is when the brown colour comes out.
Pottery- Glaze- Rutile Blue.-Cone 9-10 In this picture below, the kiln was to hot on one side, that is when the Blue-brown -cream colours comes out in the rutile blue glaze.
This bowl, with the dragon fly, is a transfer picture in the middle . Clear glaze over the top.
Outside Tenmoku glaze, the colour did burn out a bit. Nice bowl. The bowl is patchy brown colour. It is nice.
The pot below , This planter had a green glaze and a blue glaze. One side was good, to hot for other side the glaze burnt off in places. The pot it self is very rough on the outside. Nice colours.
This is my master piece. I made it by joining three small pots together. It has a lot of different colour glazer painted on. On some parts of the pot the glaze did get a bit hot, so some places it is a bit rough to handle.
This piece will be reglazed. This pieces will go back for a second firing.
That is it for on of my the second shelf gas kiln firing , learning something every time firing I Fire.
Here are the results. One of my success stories firing pottery the second time.
My master piece. I have joined three pots together. Never had cracking.
This piece has had, two glaze firings, the second time firing, I touched it up with glaze, using a brush.
This piece is 10″ high. Three small bowls joined together.
Glazers used are Rutile Blue, the colour Blue and Brown, Cream.
This Glazes has been painted on with a brush, this is where you get different colours.
Brushing Glazer on, gives different results.
White Rutile glaze, for White.
Blue is Cobalt Carbonate with a little water.
Your Glazers come out different, colours using brush on method.
This is the end piece. It is like a space man with lots of eyes and no arms.
This is my Space man. Made out of Clay.
I made this by joining three wheel thrown pots together.
In the first firing I never put enough glaze on in different spots.
My space man, I glazed two times. The hardest part was the glazes, it take a long time to dry second time. Some parts I rub with sand paper, so the glaze stuck.
You can glaze your pots 2 times, some times it works out ok,
other time your pot cracks, not a happy ending.
Don’t throw your mistakes away, fire them 2-3 times to see what happens. First time you might not like the colour of the glaze, change glazers, add more colours on top of each other, try different things.
I have a kiln at home, it is only a small kiln. I tell my self, I can make mistakes, it is mine. And yes I do make mistakes.
I like the colours you get when doing your own glazers.
Hear is what I do with my mistakes.
smash my pottery up into piecescut them with a tile cutterstick them on a terracotta pot
You can do it neater, it is a out door pot. No waste. I like it.
Happy Potting.
Please leave me a comment.
Need help ask me that Question. I might be able to help.
Find out the different colours you get when you dip your clay in your glaze mix, and when you brush in onto your pottery piece.
I am only new to pottery making and glazers. A lady who has retired from making pottery, sold me all of her pottery stuff. Gas kiln, equipment, mixed glazers, lots of minerals and more.
This is the result of one of the glazers that was already mixed, with the recipe on the lid.
Colour was Orange/Brown.
Recipe.
Feldspar 650
Dolomite 40
Whiting 130.
Ball Clay 80
Silica 100
Red Iron Oxide 60
Rutile 60.
The mix the colour looks like a dark brown.
I was using two different glazers. I wanted to see there colours together.
First I brushed on the glaze, I did two coats of the brush on. Just love the colour after firing. It did run a little bit.
This tells me next firing watch the bottom of the pot, not to thick of glaze at the bottom.
brushed on glaze.
Next I had two pots I wanted the same. First I dipped the bottom of the clay pots in a pinky glaze. The i dipped them in the brown glaze, I dipped them in the glaze slowly, and pulled it straight out. This is the results.
The glaze ran to the bottom of the potThe pink colour that was dipped about a inch from the bottom of the pot.The brown glaze only ran a little.Two pots.
The brown glaze is a nice colour. I going to add more water to the mix, and only use the brown glaze a little on the top, so it can run down a little and have more of the pink glaze on the bottom.
Well that is my story about my orange/brown glaze.
It will take a while to find out, but it would be interesting to know what colour I would get if I sprayed the glaze on.
The firing was not hot enough some colours were great, glazers ran and stuck to the shelf, other burnt out .
I was very excited to see the results. turning plain clay dishes in to pretty colours. Every time there is different colour on each shelf.
bottom Shelf of my kiln before firing.Second shelf of the kiln before firing.Third shelf of my kiln before firing.
Here are some of the results of the firing, the colours that came out.
The plate above had underglaze painted on, three times. And a clear glaze was poured over the top. Great colour of blue. the art work is not that great.This plate went in for it second firing. I brushed rutile blue on it for second firing.The results are a little better. Great seeing what colours the glaze bring out. This plate was on the third shelf of the kiln.Second firing. I put this bowl in for second firing. the green was suppose to be red. I wanted red. That is why it went in for second firing.Not a good result. After second firing. The dish was on the third shelf.This cup the glaze was burnt of the rim.No change the glaze did no stick to the rim, nice colours Brush on rutile blueThis container went in for its third firing. The glaze was running thick in places. So it was brown/black Brown.
No change
The pot split. No change to the glaze.
This glaze was nice. the pottery dish was not compressed, uneven plate bottom. Made a different in the colour of the glaze.
Well that is all for this Gas Kiln Firing, second time firing pottery, might get a good firing, your pottery might crack ,watch your glaze colours change. you will never know until you try.
Making every thing from Small Plates to Large Plates, Cup, Bowl, Planters and more.
Hand building clay pottery or wheel pottery.
Making a clay plate take a while to get to the end product. First thing you have to make something. then before it dries, you trim it to make it nice and smooth, some of my pottery is not even, I am not compressing/ smoothing out, taking the excess water away. After that you have to wait about a week for it to dry. If you put wet pottery in the kiln, it will brake, Shatter in to pieces. Broken pottery only good for the bin.
If you can not build your own pottery, have not got time. you can buy bisque wear pottery. You can paint it, or get it glazed. buy Bisque wear pottery
The large plate in the picture above, it has been put in the kiln and fired once. So it has been bisque fired, then it goes in for it’s glazing stage. Glazing pottery you have special mixers of coloured glazes that you cover on you pottery, the plate below I brushed painted lots of different colours. Lastly the pottery is put in a kiln (very hot oven) and fired to 1280 or more. Take about 8 hours to fire glazed pottery. Below the picture of the plate after glazing. I like colour.
Weight of this plate is 1200g
High 50mm, Width 210mm.
Before the pot was put in kiln, for glaze firing. You can see the glaze on it.
The pottery after the glaze firing.
It had a rutile white in the middle, then a brush on glaze on the out side and a glaze put on the top.
