Intermediate/Advanced Handbuilding Techniques - Secrets Revealed Wednesdays, 1 - 4 pm, Class #D15 Patti Nelson
From the beginner to the experienced- Find out how to make your ideas into reality!
This class will reveal secrets of top ceramic artists for more successful hand building. From building large, to building thin and strong, patch and repair, avoiding cracks, plus paper clay, staining, marbling clay and much more.
This demonstration/tutorial class is sure to inspire and stretch imagination and skills for functional and sculptural artists at all levels.
Special Projects in Slip and Plaster Wednesdays, 7 - 10 pm, Class #E16 Patti Nelson
Every had an idea and had no idea how to do it, been told it couldn''t be done? Or couldn't be done in the class that you were in?
Join us in this class with no boundaries! Learn to ask not if but how!
Designed to introduce functional and sculptural artists to the range of possibilities in working with slip and plaster. Students will learn to utilize plaster as a tool in simple and complex mold making, (slip and press molds), and as a tool for pushing the range of using clay and casting slip functionally and sculpturally. Additionally, slip will be introduced as a material to be combined with organic materials (from flowers to fabric) to create forms without limitations. Potters and hand-builders alike will find tools to expand their current work with embellishment and production methods, as well as having new ways of working presented. Whether you have ever made a mold or not, you are sure to find exciting new possibilities in this class. Pair new skills with wheel, hand-building or other methods you have loved in the past to expand your universe!
Thursday, October 27, 2011
Wednesday, October 26, 2011
Where to buy stuff...
http://www.theceramicshop.com/store/
View Larger Map
The other place to buy stuff if you want more options is Ceramic Supply of Ny & Nj, Lodi, NJ. You will most likely have it delivered if you buy it from here...
http://ceramicsupplyinc.com/
View Larger Map
The other place to buy stuff if you want more options is Ceramic Supply of Ny & Nj, Lodi, NJ. You will most likely have it delivered if you buy it from here...
http://ceramicsupplyinc.com/
Wednesday, October 12, 2011
Plaster 101
What is plaster:
Plaster comes from a naturally occurring mineral state. Pottery Plaster #1 is a Gypsum based plaster.
When it is heated to about 300 degrees f it becomes a powder. The water of crystallization has been removed.
When you re-hydrate the material, the molecules are able to take up this water, and form new inter-locking crystals. This we recognize as set plaster. These interlocking crystals are a chemical reaction and create a sponge like quality that work to absorb the moister from clay.
Heat and cold will break down this structure.
In order for plaster to have the relationship with clay that we want, it is important that it is mixed in a way that the correct crystalline structure is developed.
To Mix:
Make sure the plaster feels soft and powdery (if there are hard lumps it may have been exposed to moisture)
Measure a little less water then you think will fill up the area you want to cover
Slake the plaster into the water, not too slow, not too fast-breaking up any lumps as you go
watch for the chemical reaction to occur where the plaster starts to sit on the surface of the water (not just a lump in the middle of the plaster)
Let plaster sit in water 2-3 minutes
Agitate until you can see a finger trail in the slip that disappears quickly
Mist with rubbing Alcohol to pop bubbles
Pour steadily into your mold, trying not to create air bubbles
Agitate the mold
Mist with rubbing Alcohol to pop bubbles
You can release carefully when warm or after warmth has cooled (anywhere from 20 min- 1hour)
Wet sand to clean up and compress plaster.
Plaster comes from a naturally occurring mineral state. Pottery Plaster #1 is a Gypsum based plaster.
When it is heated to about 300 degrees f it becomes a powder. The water of crystallization has been removed.
When you re-hydrate the material, the molecules are able to take up this water, and form new inter-locking crystals. This we recognize as set plaster. These interlocking crystals are a chemical reaction and create a sponge like quality that work to absorb the moister from clay.
Heat and cold will break down this structure.
In order for plaster to have the relationship with clay that we want, it is important that it is mixed in a way that the correct crystalline structure is developed.
To Mix:
Make sure the plaster feels soft and powdery (if there are hard lumps it may have been exposed to moisture)
Measure a little less water then you think will fill up the area you want to cover
Slake the plaster into the water, not too slow, not too fast-breaking up any lumps as you go
watch for the chemical reaction to occur where the plaster starts to sit on the surface of the water (not just a lump in the middle of the plaster)
Let plaster sit in water 2-3 minutes
Agitate until you can see a finger trail in the slip that disappears quickly
Mist with rubbing Alcohol to pop bubbles
Pour steadily into your mold, trying not to create air bubbles
Agitate the mold
Mist with rubbing Alcohol to pop bubbles
You can release carefully when warm or after warmth has cooled (anywhere from 20 min- 1hour)
Wet sand to clean up and compress plaster.
Mold Making
3 things to consider:
What is the material the positive is made from? Is it
porous, non- porous, and will the heating of the plaster possibly cause and
expansion?
What does the object look like- does it have undercuts or
details that are important to maintain?
What is your plan with the final objects? Do you need
the objects to be soft for further modification? If so, you may need
additional parts of the mold for easy release.
1. Decide if you want to use a
clay bed to lay your object on or if you want to lay it directly on the surface
(the clay bed is easier to seal.
2. Soap your object if porous.
Polish it to a silky finish.
3. Determine where your walls
need to be for each section before you start. This will ensure that you
are working smart not hard. Use a clay maquette or a sketch to help
you. If you don’t care about the object you can also use a sharpie
directly on the object.
4. Using slabs, create walls
for each section. Be careful to seal each section (rubber finger tools
work great for this.) Mix and pour plaster one section at a time. Let each
section set up. Make keys, then pour the next section.
5. Use the amount of clay it
takes to properly caulk any cracks. Wipe away any extra clay. A
small amount of clay can seal without creating a large seem.
6. After the mold has been
poured and has set, gently vibrate the mold apart. Remove the
positive. Put the mold back together for cleaning so that you don’t
inadvertently clean the fettle lines (the place where the mold pieces meet up
on the interior of the mold. )
Sanding the mold compresses the mold, gets rid of plaster
that might chip off, and helps it to last in the future.
Slip:
Even store bought slip should be sieved before use.
This eliminates lumps that will have to be sanded out later and allows even
water distribution.
Deflocculate: To literally break up the “flock” of clay
particles by creating a negative charge and causing particles to repel each
other. This allows us to add less water with more fluidity and allows
particles to bond with better compression and with out air bubbles. We
add this deflocculant to slip (Darvan or Sodium Silicate)
Coddle: The objects which contain our plaster while it sets
around the object we are casting. Sometimes Aluminum Flashing, or boards
we clamp together.
Fettle: The seam of the mold.
Fettle Line: The line of an object where the undercut occurs
(often still visible on plastic cast objects, such as pens)
Undercut: The point where if an immoveable object (such as
set plaster) is wrapped around it will become locked and cannot be removed.
Key: the small indentation that keeps a mold from sliding
apart. Two primary types: Standard Keys and Slide Keys.
Mixing Slip
When mixing slip there are a few considerations to take into
effect:
Start with about 5 % warm water.
Add your deflocculant to the warm water. Because the defocculant is likely to be less then 1% of the recipe, it is important to measure it carefully either by weight or by volume.
Beginning with the lightest ingredient mix ingredients one at a time to avoid pancaking later.
Every clay/slip will have a clay, a flux (melting agent), a glass maker, and most likely has a filler. Sometimes ingredients will do double duties.
Kaolins (porcelains) will be lightest, ball clays next, other clays next, then things like talc, silica, and feldspars are likely to be the heaviest. You can do a simple touch test to determine density.
Sieve and add water to get to desired consistency based on your needs. I recommend double sieving at about a 40/60 and 80/100.
When recycling slip, its best to dry it out completely then add warm water and double sieve. If you have used a Darvan as your deflocculant, you will not need to add more. If you have used sodium silicate, recycle your slip as above, then test the webbing properties. If it is not webbing properly, add sodium silicate a tiny drop at a time. Go slow with this and be careful not to add too much water until the deflocculation is complete. To avoid this, use a Darvan.
Tips:
Over deflocculation and under deflocculation look almost the same. Vinegar will cut deflocculation, go slow and if in doubt, revisit it the next day.
I have found that slip is best after sitting for a day.
Start with about 5 % warm water.
Add your deflocculant to the warm water. Because the defocculant is likely to be less then 1% of the recipe, it is important to measure it carefully either by weight or by volume.
Beginning with the lightest ingredient mix ingredients one at a time to avoid pancaking later.
Every clay/slip will have a clay, a flux (melting agent), a glass maker, and most likely has a filler. Sometimes ingredients will do double duties.
Kaolins (porcelains) will be lightest, ball clays next, other clays next, then things like talc, silica, and feldspars are likely to be the heaviest. You can do a simple touch test to determine density.
Sieve and add water to get to desired consistency based on your needs. I recommend double sieving at about a 40/60 and 80/100.
When recycling slip, its best to dry it out completely then add warm water and double sieve. If you have used a Darvan as your deflocculant, you will not need to add more. If you have used sodium silicate, recycle your slip as above, then test the webbing properties. If it is not webbing properly, add sodium silicate a tiny drop at a time. Go slow with this and be careful not to add too much water until the deflocculation is complete. To avoid this, use a Darvan.
Tips:
Over deflocculation and under deflocculation look almost the same. Vinegar will cut deflocculation, go slow and if in doubt, revisit it the next day.
I have found that slip is best after sitting for a day.
Paper Slip
Paper slip is a good solution for surface tension cracks.
If you are experiencing cracking in your process, a small amount of paper
can help your situation.
It is important to note a couple of things:
Adding paper to clay may strengthen it while wet, bone dry and during firing, but may weaken it in the final fired state.
If the paper is not disintegrated well it can add texture, you may or may not want this.
Paper will rot, and smell.
Paper added into slip can make it very difficult to re-sieve.
For the above reasons, I recommend using the minimum amount necessary, and to mix paper slips in small amounts at a time to negate the need to re-sieve that batch of slip.
Use cheep toilette paper. It has less glue and breaks up easily. Tear it up very small, a food processor can work great on dry paper.
For a gallon of slip, 15-20 squares can be plenty.
Add it to warm water with a tea spoon of vinegar. I like to let it sit over night. Blend it with a hand blender until paper is completely dispersed in the water. Then just add to well sieved slip, blend well, and use as normal.
It is important to note a couple of things:
Adding paper to clay may strengthen it while wet, bone dry and during firing, but may weaken it in the final fired state.
If the paper is not disintegrated well it can add texture, you may or may not want this.
Paper will rot, and smell.
Paper added into slip can make it very difficult to re-sieve.
For the above reasons, I recommend using the minimum amount necessary, and to mix paper slips in small amounts at a time to negate the need to re-sieve that batch of slip.
Use cheep toilette paper. It has less glue and breaks up easily. Tear it up very small, a food processor can work great on dry paper.
For a gallon of slip, 15-20 squares can be plenty.
Add it to warm water with a tea spoon of vinegar. I like to let it sit over night. Blend it with a hand blender until paper is completely dispersed in the water. Then just add to well sieved slip, blend well, and use as normal.
Cones
Cone Temperatures
10 (High fire) 9 8 7 6 (Mid) 4 3 2 1 01 02 (high bisque) 03 04 (low fire) 05 06 07 08 09 010 (low bisque) ... 018 019 020 (Enamle, Luster, China)
cone chart
10 (High fire) 9 8 7 6 (Mid) 4 3 2 1 01 02 (high bisque) 03 04 (low fire) 05 06 07 08 09 010 (low bisque) ... 018 019 020 (Enamle, Luster, China)
cone chart
Intro to our blog
Hi Everyone,
This is the blog that will carry technical information, images and notes from Wednesday classes at Cheltenham Center for the Arts.
Please feel free to create posts, make comments, and upload images.
This should be an interactive online extension of class.
Both Handbuilding and Special Projects will share this blog, because much of our information can be useful to both groups. I will tag all posts for the class they are relevant to, but feel free to read all!
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