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For Amaco, Laguna and Spectrum glazes (other than Novas), when you purchase them in liquid form (pints, gallons, etc) they are are formulated for brushing. When you purchase them in dry form, they are formulated for dipping, pouring or spraying. Coyote glazes (and Spectrum Nova glazes) are formulated the same whether purchased in liquid or dry form.
As a general rule of thumb, for 1 lb of dry glaze powder, use 11 ounces of water for dipping glaze, 8 ounces of water for spraying glaze, or 7 ounces of water for brushing glaze. Or, 25 lbs makes about 3 gallons. This is only a starting point.
To use a dry glaze for brushing, a brushing medium, such as CMC or glaze medium may be added. CMC acts as a binder and allows the glaze to flow smoothly. If you purchase CMC or brushing medium in dry form, it is best to add those to your dry glaze before adding water. Or the liquid forms of CMC or brushing medium will mix more readily into glazes that are already mixed.
To mix a dry glaze, first add bentonite to the dry glaze to keep it in suspension and increase the drying time. Not all glazes will need this. It depends on the composition. Bentonite is mixed at approximately 2 grams (.0044 pounds) per pound of dry glaze.
Measure water into a clean plastic bucket. Mix the measured amount of glaze into the water as best as you can. Then pour the mixture through a sieve into a second bucket, pushing the clumps through the sieve with a rib or other tool. Repeat several times.
Note: Glaze recipes sometimes specify a mesh to use, and that will affect the outcome of the glaze. Otherwise, for glazes, 80-100 mesh are most common (lower numbers are usually for mixing slips).
Optionally, a hydrometer could be used to check the viscosity of the mixed glaze. The hydrometer reading should be approximately 900-1000 for dipping, 1500-1700 for spraying, and 2200-2500 for brushing.
Let the glaze sit for 24 hours, remix, then use.
Glaze should be stirred often, as contents can settle during use. If the glaze thickens over time, you can usually just add water.
Some people find that if they use a power mixer they don't have to sieve their glaze. The sieving process accomplishes 2 things.
1. Makes sure the glaze is well mixed.
2. Gets rid of lumps.
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Here are a few handbuilding tips we've come across in our travels. Have a few you want to share yourself? Drop a comment!
1. Having trouble with clay sticking to your molds, rolling pins, and canvas?
- Use pantyhose to cover molds, rolling pins, etc.
- Sprinkle the surfaces with cornstarch. It will burn off in the kiln.
- Cover items with Saran Wrap or newspaper.
- If you're using the slab roller a lot, the canvas can get wet and cause sticking. Use separate pieces of cloth (old sheets are great and you can get them at garage sales for 25 cents) or thick plastic instead of placing the clay right on the canvas.
2. To keep tiles and other pieces of clay flat as they dry, sandwich them between pieces of drywall. You can stack many layers this way.
3. To support your slabs while handbuilding, try cutting your templates out of roofing paper (tar paper) or cardboard. They will support the slabs so you can assemble them while they are still soft. Keep it attached until the clay hardens, then peel off.
When's the last time you did throwing exercises? They are great for warming up after a period without throwing, for improving your skills to the next level, and for getting ideas when you are out of them. Here are some great exercises.
Timed throwing is especially good when you are in the habit of obsessing over every piece. Weigh out 10 equally sized balls of clay. They should be an amount you can rather easily throw (don't use more than you can easily center).
Choose a shape (cylinder, bowl, etc.) Get a timer and set it for 3 minutes. Start the timer. Center and throw the first ball of clay. Stop when 3 minutes is up, cut off the pot, and rest for a minute. Start the timer and repeat 10 times.
At least every few pots, you should take your cutoff wire, run it beneath the piece half way, then pull right up through the center of the pot, cutting it in half. Observe where your walls are thick and thin.
Even if you don't do timed throwing, it is very useful to take equal amounts of clay and try to make multiple pieces exactly the same. You will need this skill for doing sets (ie. dinnerware), but it is also useful for developing technique. Don't try to do it without a scale... If you're like most people, you'll find that you are not very good at eyeballing equal weights!
In Japan, apprentices throw thousands of copies of the same shape, and are not allowed to progress to a new shape until they have mastered that one. One of their early shapes is a production sake bottle, where it is important for the size to be right so the bottler isn't giving away too much liquor nor cheating the buyer.
Throwing on a Theme
This is good for exercising your creative juices and learning good design. Starting with the same amount of clay, make similar items but find a way to differentiate them slightly. Most professional potters work this way, exploring a shape until they have to push it to its limits.
Follow Along with a Book
For example, "Wheel Thrown Ceramics" by Don Davis has both projects and photos of thrown pieces. A great book for the intermediate potter, it focuses on thrown and altered forms, and techniques for capturing the spontaneous fluidity of clay. Follow along, first duplicating each form, then expanding in it. Again, it is best to do several of the same form before moving on to the next.
We sell a variety of throwing books. If you find yourself having difficulty duplicating a shape, you may need more demonstration than a book can give. In this case, a good set of DVDs on throwing might be more the way to go.
You may try these exercises knowing that you won't keep any of the pieces. Just cut them off the wheel, re-wedge the clay, and use it again. Some people find that knowing they won't keep the piece allows them to be more experimental and take more risks.
So next time you're stuck in a rut, or not sure what to make, do some exercises and you'll see how much better your work gets!
If you've never used a slab roller, it can seem daunting. But it's not as hard as it looks. Follow along with the steps below and the video above and get rolling!
How to Use a Slab Roller
Step 1: Wedge clay.
Step 2: Clear the surface of the slab roller, remove one spacer from under the rolling surface and lay canvas under and on top of your wedged clay.
Step 3: Begin rolling. Don't try to roll faster than necessary and if the roller jams, do not force it; back it up and figure out what it is catching on (your clay may be too thick).
Step 4: Flip your slab over, rotate it 90 degrees and reinsert the spacer under the rolling surface.
Step 5: Roll again.
Step 6: Uncover, smooth with a rib and transfer to a board.
Here is a common scenario. A potter sees a piece with a glaze they really like. They get the recipe, mix up a batch, and are disappointed with the results. Their glaze looks nothing like the one they originally saw. If this has happened to you, you know the frustration.
This happens for a few reasons, but most of all by what has influence over the glaze itself during firing.
A Glaze Is Affected By:
- Final temperature. Even if fired to the same Cone, the temperature may vary from one part of the kiln to another, or two people might interpret the bending of the Cones differently.
- Rate of change in temperature, particularly cooling rate. This is a main reason why glazes look different when fired on a whole piece than when fired in a test kiln, because the smaller test kilns usually cool faster.
- Clay bodies. Color as well as the materials in the clay body. For example, iron in a clay will often cause spotting through the glaze, or will act as a flux causing glazes to melt earlier).
- The thickness or thinness of the application or the method of application (sprayed, dipped, or brushed).
- Variations in materials (Glaze materials are taken from the earth, and their compositions are not pure. There is always some variation from batch to batch, and sometimes this variation is enough to affect the glaze in a substantial way).
- Atmosphere: The amount of oxygen present or not present (reduction).
- The presence of other glazes nearby.
- Particle size differences. If a material is available in 200 mesh and 325 mesh, these will melt differently and give different effects.
- Mixing and screening. How well the materials are mixed and to what mesh they are screened will effect the final result.
- Venting. Whether and how much a kiln is vented can affect the final firing.
As you can see, there are many factors, so it is not surprising that it is hard to replicate a glaze.
When it comes to selecting a clay body, the possibilities seem endless. There are so many different formulations and variations, colors, textures, workability, throwability (is that a word?). It can get confusing to select the perfect one. Which is why most potters I know, including myself, don’t settle on just one.
I use both earthenware and stoneware in my work. I gravitate towards white stoneware (Laguna WS-4 is my favorite) but I also dabble in brown and black stoneware and also earthenware like Laguna EM-210 when the project warrants low-fire glazes and underglazes.
So what’s the difference between earthenware and stoneware? Here’s a quick breakdown:
- Low-fire: cone 06-3 (1850-2135 degrees).
- Slightly porous, even when fired to maturity (water will soak into it if not glazed or sealed).
- Low-shrinkage from wet to fired states.
- Great for planters, oven steamers/garlic roasters, kids projects/art class and decorative items.
- Not so great for dishware as it is not as sturdy as stoneware or porcelain and is prone to chipping and staining.
- Mid-High fire: cone 4-10 (2160-2372 degrees).
- Non-porous when fully vitrified (fired to maturity temperature recommended by clay company).
- Widely used for dishware and functional items as well as sculpture and decorative pieces.
- Range of shrinkage depending on specific clay composition, but your piece WILL get smaller when you fire it.
I sat at a desk for many years as part of my non-clay life, and I am a combination of very active and apparently clumsy, managing two relatively big sports-related injuries between 2006 and 2011. Added to that, I’m tall, long-waisted, and lanky, so sitting, be it (the worst) in a vehicle or (the best) at the pottery wheel, makes me feel fidgety, too tall, and like I’m being collapsed like a folding chair.
When I found studio space in 2011, I decided to buy Pacifica’s “B” leg extensions along with my GT800 pottery wheel so that I could throw standing up.
There are so many tools on the market for which to carve and texture clay that it's sometimes difficult to choose specific ones that are right for your purposes. In this article, I will show you specific tools that I love and the projects they were used for.
Kemper Tools, especially the stiff texture brushes, Pro Line trimming tools and sgrafitto tools, are my "go-tos." I have worn through a few sets because I often scrape back layers of glaze on bisqueware. I apply the glaze in the order that I need, transfer my drawing on the top dried coat, and begin scraping.
I have taken a lot of risks with different underglazes and a variety of glazes from Duncan, Laguna, Mayco, Spectrum, and Amaco, and have found these tools add texture with a light touch. They are also great for scoring greenware.
These pieces couldn't have been completed without these tools (and yes, I draw upside down).
To Vent or Not to Vent?
Recently I was asked by a fellow potter if I use a kiln vent system. I do. I use the L&L Vent-Sure Kiln Vent System and I love it!
But that got me thinking...I know plenty of professional potters that don’t use vents when they fire, even for glaze firing, and their work comes out perfectly. It’s been so long since I purchased my first kiln and the vent system. I used to have my kiln right in the studio with me – so not using a vent was out of the question. Nowadays, my kiln is in my attached garage.
So why do I continue to use a vent system? Here are three reasons:
Reason 1: Safety
The fumes that come from a firing, even a bisque firing, are not good for you to breathe in. Since my kiln is in our attached garage, it’s really important for me to make sure the fumes go outside and not back into my house.
Reason 2: Even Firing Temperature
When you use a kiln vent system, the air is pulled into the kiln and this helps to even out the temperature during a firing. The air is circulated constantly so the temperature in all areas stays within a few degrees difference. This is important for accurate firing times and final temps.