Frequently Asked Questions
Frequently Asked Questions
- Safety is your first concern. Either unplug the kiln or isolate on wall and on mains distribution board. If a locking device is provided, lock the switch off. In a domestic environment, advise the family of what you are doing, in particular to the switches, which have been switched off.
- Remove the covers exposing the connections to the elements.
- Make a careful note of how the elements are connected, and then disconnect all the wires to the tails of the elements, marking them appropriately for the positions to which they were attached. Old elements tend to become very brittle and will probably break once you attempt to remove them from the grooves. Special care must be taken to protect the groves from mechanical damage.
- If the elements were pinned previously then it would be recommend that you pin the new elements in similar positions.
- You will need a bolt cutter to trim the tails of the elements, which are normally supplied over-length. Cut them to the same length of the old ones.
- Re-attach all your wires making sure that you fasten the wires to the element tails very firmly.
- If you are equipped to check the current drawn or if you have a friend who is able to do this for you, it is a good idea to compare the specified current versus the elements that have just been replaced.
- Replace all covers.
- Then it is necessary to oxidize the elements – this is achieved by firing the kiln empty to 1100ºC and soaking for 3 hours with the bungs open. This process ensures that the elements generate an oxide layer, which protects them from the atmosphere.
NB. A good idea would be to compare your new elements to the elements in the kiln prior to removing the old ones, ensuring that they are visually similar.
Formula is :
((kW rating of the kiln) x (cost of electricity per kW) x (hours of firing time)) x 60%.
1. KW rating of kiln should be on specification plate at the back of your kiln.
2. Cost of electricity per kW – this should be on your electricity account or electricity recharge slip (e.g. 0,20 – 0.36c per kW).
3. Time taken to reach temperature in hours.
4. Then 60 % x all of the above.
In Short :
R3.30 per kw rating of a kiln i.e a 10kw (+/- 8 ft cubic foot kiln) would cost
R33.00 this is based on R0.55c per kWh and a typical firing of 10 hours.
Send by fax or e-mail a drawing detailing the following information. 1. if a specification plate is visible notate the current drawn, kW rating and Voltage of the kiln, and if the model number is available/ serial number. 2. length of element and number of grooves it occupies. 3. indicate whether tails are twisted or single and the length. 4. measure outside diameter of the coils. 5. thickness of wire – use a vernier for accuracy, as the nominal difference between wires can be 0,1mm. 6. your name and contact details. We can typically have elements made within 48 hrs of confirmed order.
CONE DRIVEN ELECTRIC WHEEL
1. WHISPER QUIET, POWERFUL 0,37kW MOTOR.
2. TRIED AND TESTED SMOOTH CONE DRIVE
3. COMFORTABLE SEAT
4. EASILY CLEANED FIBREGLASS BASIN WITH DRAIN AND PLUG
5. ALUMINIUM WHEEL HEAD
6. AUTOMATIC "SWITCH OFF" ON PEDAL RELEASE
7. SIMPLE AND INEXPENSIVE TO SERVICE.
ELECTRONIC BELT DRIVEN WHEEL
1. WHISPER QUIET, POWERFUL 0,37 kW, THREE PHASE MOTOR DRIVEN THROUGH A SINGLE PHASE ELECTRONIC CONVERTER.
2. HIGH TORQUE THROUGH THE ENTIRE SPEED RANGE.
3. FLEXIBLE RIGHT HAND, LEFT HAND OPTIONS.
4. FULLY MOBILE FOOT PEDAL
5. CAPABILITY OF CONSTANT SPEED AND IDEAL FOR DECORATING AND TRIMMING.
6. VERY FEW WEAR COMPONENTS RESULTING IN SIMPLE AND INEXPENSIVE SERVICING.
7. COMFORTABLE SEAT
8. EASILY CLEANED FIBREGLASS BASIN WITH DRAIN AND PLUG ALUMINIUM WHEEL HEAD
Fax or e-mail your order, including your address, we will then contact you with the total price, weight and availability/ dispatch date. You then make payment via credit card or electronic transfer, fax us proof thereof, and then we dispatch either by post, courier or rail depending on size, weight and costs. Transport costs are for the clients accounts.
Yes, alternatively payments can be made directly into our bank account.
Crawling occurs when a glaze separates into lumps and beads. Dust and/or grease on bisque can repel glaze, causing crawling. For this reason always wipe bisque with a damp sponge before glazing. Bisqueware that has been standing for a long period should ideally be re-bisque fired. Some glaze ingredients (including zinc, colemanite and opacifiers) are prone to crawling when applied too thickly. Some underglaze colours when applied too thickly could have the same result.
In modern times, cones are still a very important tool in a potter’s armoury. It is the only definitive measure of heat work done on pottery.
With the current regime of power failures, without a cone in your kiln you will not know whether your pottery reached temperature unless it is badly under fired. More recently we have had glazes from prominent suppliers, which have been problematic. It is useful to bench mark good firings with cones and to save the cone results. If you are experiencing unsatisfactory results, cones will quickly tell you whether the kiln is misbehaving or whether the glaze is misbehaving. If the fired results of cones significantly differ to your benchmark then look to your kiln for the cause. If the fired result of the cones is the same as your benchmark look to your glazes and or clay body for the cause. It is useful to place cones next to your thermocouple and in areas where you get your best results, as these are your litmus tests.
In modern times, cones are still a very important tool in a potter’s armoury. It is the only definitive measure of heat work done on pottery.
With the current regime of power failures, without a cone in your kiln you will not know whether your pottery reached temperature unless it is badly under fired. More recently we have had glazes from prominent suppliers, which have been problematic. It is useful to bench mark good firings with cones and to save the cone results. If you are experiencing unsatisfactory results, cones will quickly tell you whether the kiln is misbehaving or whether the glaze is misbehaving. If the fired results of cones significantly differ to your benchmark then look to your kiln for the cause. If the fired result of the cones is the same as your benchmark look to your glazes and or clay body for the cause. It is useful to place cones next to your thermocouple and in areas where you get your best results, as these are your litmus tests.
In modern times, cones are still a very important tool in a potter’s armoury. It is the only definitive measure of heat work done on pottery.
With the current regime of power failures, without a cone in your kiln you will not know whether your pottery reached temperature unless it is badly under fired. More recently we have had glazes from prominent suppliers, which have been problematic. It is useful to bench mark good firings with cones and to save the cone results. If you are experiencing unsatisfactory results, cones will quickly tell you whether the kiln is misbehaving or whether the glaze is misbehaving. If the fired results of cones significantly differ to your benchmark then look to your kiln for the cause. If the fired result of the cones is the same as your benchmark look to your glazes and or clay body for the cause. It is useful to place cones next to your thermocouple and in areas where you get your best results, as these are your litmus tests.
In raku often one uses more than one shelf when packing the kiln.
When the time comes for removing the fired items while still red-hot, tongs are used. In order to remove a shelf quickly with tongs, holes are made in the shelf in order that the tongs can grip the shelf easily.
Mix up a bit of batt wash with water until it is like milk in consistency. Rather make it too runny than too thick, as, if it is too thick, it will crack off your shelf before you even put your shelves in the kiln. Brush this runny mixture of Batt Wash onto one side of your kiln shelf with a soft brush. Allow this to dry. You will still see some of the shelf colour through the Batt Wash. Apply another coat of Batt Wash to the shelf and allow it to dry. You will probably need to apply a third coat.
You will know when you have applied enough when you can no longer see the colour of the shelf through the Batt Wash and your shelf now appears white.
Once you have done this, leave your Batt Washed shelves to dry overnight.
The shelves will have soaked up water with each application of Batt Wash, and you do not want to fire your shelves in the kiln when they are wet, as they may crack. For the same reason, fire your shelves in a bisque firing, rather than a glaze firing – i.e. fire them slowly, rather than fast. You will be able to use your shelves for many firings - up until the time that the Batt Wash starts to crack off the shelves. When this happens, scrape it off, turn your shelf around, and apply new Batt Wash to the other side of the shelf.
Should you apply Batt Wash to the underside of your shelf, when it gets to the stage where the Batt Wash starts to crack off, it would land on your pieces in a glaze firing and ruin the glazed pieces.
1. To mix plaster of paris you need a ratio of 1.2kg of plaster of paris to 1litre of water (or 1kg plaster of paris to 833ml water).
2. Pour water into a bucket, sieve plaster of paris quickly through your fingers into the water, to disperse powder evenly over the surface of the water.
3. When the plaster of paris forms a peak in the water let it stand for approximately half a minute (to allow the plaster of paris to absorb the water).
4. Stir mixture vigorously with your hand until all the lumps have dissolved.
5. Let mixture stand for a few seconds until it becomes a creamy liquid.
6. The plaster is now ready to pour into the mould.
The best way to do this is to peel back the top canvas sheet and to place a wooden board or batt on top of your clay slab, then turn the boards over and your clay slab will now be on top of the wooden board or batt. Remove the drive board, your clay slab is ready for cutting.
KILN WASH
Kiln forming techniques require separators between the glass and the shelf
or mould on which it rests during the heating process. These separators have
different generic names - kiln wash and batt wash are two.
There are a number of brands of kiln wash. All of them contain two main
ingredients - alumina hydrate (sometimes called slaked alumina) and kaolin
( also called china clay). Different producers use these ingredients in
various proportions. A number also include a colourant that changes when
fired above certain temperatures to indicate the material has been dried.
An important thing to remember is that the kaolin changes its composition
once it is fired over 700C. This change causes it to stick to the glass on
subsequent firings. Thus, it is essential to change the kiln wash after
every firing that reaches that temperature or higher.
It is possible to apply a fresh coat of kiln wash over the old one to save
time. However, as soon as the kiln wash flakes you must scrape off all the
old kiln wash and apply a new coat to the bare shelf or mould.
Posted by Stephen Richard on http://glasstips.blogspot.com/2009/07/kiln-wash.html
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