Idaho potter Brad Sondahl's Pottery Tips

Favorite ways I do things:
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Clay recycling
Hand glaze stirrer
Drill Powered Mixer
To keep glazes from settling
Glaze pourer
Ready made tools
Make your own wedging table
Trimming Tools
Embossing stamps
Throwing Ribs
Throwing Sticks
Sponge on a stick
Hole Puncher
Cleanup Scraper
Glaze thickness tester
Wheel Powered Grinder
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The following are related pages on my website:

Guided Tour of Brad's Pottery Workshop
For a large list of original Sondahl Pottery glazes (Cone 8-10 Oxidation), click here
Sondahl's short guide to crystalline glazes
Sondahl's home guide to Electric Kilns
Collection of my Ceramics Monthly  and Pottery Making Illustrated Articles and other pottery thoughts
Multiply your glaze tests with my Glaze Hybridization system page
Brad's Main  Index
Sondahl Pottery Samples Page

Here are the Pottery Tips:

Clay recycling: Dry the scrap clay on the bisque kiln or in kiln room (this loosens clay particle bonds--critical step). Slake (wet) it by pouring water over scraps in 5 gallon bucket. Let it sit for awhile, then poke with stick to mix and debubble it. Pour off excess water into another bucket. Leave in kiln room till dry enough to spread on boards. Wedge when workable, store when proper consistency.
Best hand glaze stirrer. Skimmer by Ekco.  Sort of stainless steel slotted wide spoon gadget. Cheap. Available in kitchen supply areas of larger stores. Helps with stirring--identifies if lumpy by lifting sample out. Helps with sieving also.

Good Drill Powered Mixer: Weld a 5/16 to 3/8 " steel rod onto the middle of 5 links of chain.  Make it long enough to fit in a 5 gallon bucket-- or whatever size glaze buckets you use.  3 links of chain work for small buckets.  Hold at an angle to get the heavy stuff towards the top. This also works great for getting glazes through the sieve, if you can pour by tipping the bucket with one hand while stirring with the other (if you can't, find a friend).  It might be worth it to make a shorter one  with 3 links just for sieving.
If you don't know a welder, look for paint mixers at your local hardware...

To keep glazes from clumping: Epsom Salts solution: by volume 3 parts hot water (helps dissolve) to one part Epsom Salts (available drug and grocery stores cheaper than pottery suppliers.), Add 1 1/2 cups of Epsom Salt solution to 4 gallon batch of glaze..

Handy Glaze Pourer: The green straight handled cups that come with dry detergent can have the handle bent straight down by heating over a flame.  They then will hang over the edge of your glaze bucket, and they pour a nice small stream from the corners of the cup.

Best Ready-made Tool helpers: Dremel high speed rotary tool (available in hardwares) with Aluminum Oxide cone or round tips.  Great for grinding off poky bits from glazeware (but refire glaze to smooth it again...)
For glaze test and slip mixing, get an old electric blender and mayo or canning jars. Screw the cutting assembly on the jar with what you want delumped, and blend away. Keep a hand lightly on top as you blend, to keep the jar from being vibrated off.  I never sieve glaze samples--the few tiny lumps don't matter on the test, and a lot of time is saved...

Into the Potter's House

Here's the text from a how-to book I started writing on pottery, at a publisher's request. It wasn't the book they wanted, but it was the book I could write..  If you think it's really a worthwhile endeavor, contact me (especially if you are an editor ;-).  A lot of these ideas are gleaned from Ceramics Monthly or the Web, some are mine.  Thanks to the anonymous donors.

Chapter 2. A potter's tools--making your own...

How to make your own wedging table, bats, loop tools, trimming tools, plaster stamps, throwing ribs and sticks, sponge sticks, hole punchers, scrapers, and glaze density tester. Also a practical grinding disk to attach to your wheel head.

This chapter will show you how to make many basic pottery tools. But first you may wonder--why bother? Every pottery supplier stocks hundreds of different tools by dozens of makers. There are several good reasons to make your own tools. Most homemade tools are cheaper than manufactured ones, sometimes even free... Also, few people live near enough to a clay supplier to get new tools or replacements easily, so it can save a lot of effort to make your own tools. However, the most important reason to make your own tools is that they will be a unique extension of you. The plaster stamp that you hand carve, even though it may not be as uniform as a commercial product, will better help you to express yourself. Some of the ideas are for improved comfort, such as the following multilevel wedging table.

Wedging Table The table where clay is kneaded must be sturdy and may benefit from being screwed to the wall. Other design considerations include: comfortable height, absorbent surface, cutting wire, and sufficient space to set scale and pan for the measured lumps of clay. My own answer to these criteria is a multilevel table, as illustrated below:

A multilevel wedging table can help to relieve back pain. When wedging larger lumps of clay, a lower surface is helpful, as wedging is done more from the hips then. For smaller amounts, the upper arms are used, and a straighter stance is helpful. The diagram has suggested heights which I use. I'm six feet tall, so you may wish to adjust according to your own height.  A good heighth is where your knuckles end when standing up. The width and depth for the plan is left up to the individual. Also included is a storage area (which I use for recycled clay), plywood backing (for structural strength), and a cutting wire, tightened with a turnbuckle (available at hardwares). Used steel guitar strings make good cutting wires, as does heavy weight fish line. Many surfaces are suitable for wedging tables. Poured plaster is a classic, but I've always avoided it, as bits of plaster can come loose and cause lime popping in clay. Plaster is better with a stretched canvas cover secured over it. I prefer raw exterior grade plywood, which is surprisingly good by itself, and also improved with canvas.

Tip: When stretching cloth over a rectangular surface, staple the four middles of the cloth to the board first, then pull toward the outer corners as you staple. The result will be wrinkle free. I learned this in an art class for stretching canvases, and it's probably the most valuable thing I learned in college (it comes in handy when replacing screen windows in the home, too.)

Bats Some folks use the cutouts from formica countertops (obtained from cabinet shops) for bats, but they seem a bit bulky to me. I recommend quarter-inch tempered masonite bats, cut into several diameters. (Masonite is available at most lumber yards.) Most of the pots I make can be thrown on 10 inch bats, but larger plates and bowls can use 12 or even 18 inch bats. Cutting them with a saber saw can be tedious, but if they are properly coated, will last a long time. When making them, a compass, or string tied on a pencil secured with a thumbtack, can be used to make the master, or even tracing around your wheel head. After the master is cut with a saber or band saw, it can be traced with a pencil onto the rest of the masonite. Linseed oil, shellac, and polyurethane are good finishes to help prevent degeneration of the masonite. You can get your wheel head drilled and tapped at a machine shop to add bolt-type pins to secure the bats to the wheel head. Brass bolts will be more easily removable later, if needed. It is also quite practical to secure bats with clay on the wheel head. One or two coils are placed in concentric circles on the wheel head, and then are centered smooth and level. The bat is placed centered on top, and patted to create suction. Gentle lifting will release, or occasionally a tool can be inserted to break the suction. The coils must be rewetted as new bats are attached.

Shown are pearshaped and small loop tools (which can be made at home), Japanese style, homemade L shape from sweeper brush, and pentip holepuncher.
Loop and other trimming tools.In making tools, first let's consider materials. The most common materials for pottery tools are wood and steel. For durability sake, wood tools which contact clay benefit from being hardwood (oak, maple, ash) as opposed to soft wood (pine, fir). If they are just handles for metal tools, this is not so important. Steel also comes in several varieties, but the important point for us dilettantes is whether it is bendable (malleable) or spring steel. While shaping a tool, it's nice for the steel to bend without breaking. However when using the tool, some force is applied, and we'd prefer it to stay as shaped. Both of these goals can be accomplished by heating the metal. When hot, the steel will bend easily (though it must be handled carefully). By plunging the finished shape in cold water, the steel becomes more springlike and then resists bending.

Tip: If the steel you start with bends easily, shape it without heat. Then heat and plunge it to change it to spring steel.

Common sources for steel ribbon include steel strapping tape (available free at lumberyards, where it is used to wrap bundles of lumber), and street sweeper brushes. Any town which uses the big street sweeper machine litters these liberally. Once you know what to look for, they're easy to spot on the street (my son came home with a dozen on a short walk from school). Coathangers can also be used, but benefit from being pounded flat between a hammer and a vise or other hard surface, to make them more able to cut into clay.

Tip: Steel strapping tape is bendable, but may need snipping thinner with tin snips. Sweeper brushes are spring steel, and need to be heated to be bent)

The (missing) picture series shows the process of making a loop tool. Some suggested shapes are also shown. (Not included at this time) Captions for picture series: 1. Wood handle is cut from dowel, sharp edges are smoothed. 2. Loop is heated and bent to fit with needlenose and regular pliers. 3. Loop is plunged to change to spring steel. 4. Loop is attached to dowel with glue, and many windings of fish line, tied. 5. Useful loop tool shapes.

Tip: Visualizing and actually bending the loop shapes can be tricky. Make a life-size drawing of the shape you are trying to make, and hold the loop over it to compare as you bend it.

Open ended trimming tools.Loop tools, being secured at both ends, are very stable in use, but cannot be used for scoring or cutting. The Japanese style open ended trimming tool, being a bar of steel with right angle bends at each end, can be used to both trim and score. It also is made from heavier metal, and will prove more durable than loop tools. The material should be strap steel, approximately 8 inches long by one inch wide, 1/8 inch or less in thickness. One inch of each end is inserted in a vise, and then bent over to a right angle. The tool will most likely make a U-shaped cutting area if bent by hand. If a more sharp cutting area is desired, a hammer can pound the bend to a sharp right angle bend. The resulting shape, diagrammed below, is the tool. It is held between the two ends, with either end pointed toward the pot. The handle area can be wrapped with duct tape for more comfortable holding. If the steel used for the tool is thick, the cutting area can be sharpened with a file or grinder before use.

Tip: To sharpen tool, hold tool at angle of use, and grind or file the part which first contacts the clay.. This is the part which would get worn away with use. When the tool is sharpened this way, use will maintain its sharpness. Also, the bend need not be 90 degrees. If it splays out (up to 135 degrees), it is more comfortably held for cutting into a foot.
Update: My favorite trimmer currently is the Streetsweeper brush L-shaped trimming tool, due to its low drag, and ease of manufacture (pictured above).  Drill a hole slightly smaller than the streetsweeper brush in a dowel or bar of wood.  Pound in straight, until tight.   Make 90 degree bend while heating blade over flame..

Plaster StampsOccasionally a repeated design can be a good thing. Plaster stamps are one easy way to repeat a design, in soft clay. Plaster works well to copy a clay master. It can also be carved easily to become the master itself. Being slurpy, plaster needs a mold to contain it, and a way to free the plaster from the mold (that is, release). The following procedures are the way I make plaster stamps.

Clay Master Molding (Missing) Photo Sequence: Making a clay master mold (not currently available) Caption: In order to make a commemorative stamp for a church centennial plate, I started with a photo of the church, and drew a grid on the photo. I copied the grid onto a slab of clay, and drew an outline on the clay, using the grid as a guide. I then added clay to the slab to turn the drawing into a bas relief. When the sculpting was complete, I centered the slab on the wheel, and cut the master into a circular motif. A slab of clay was added around the circumference, to form a container to fill with plaster. After allowing the clay to stiffen, plaster (obtainable at hardwares and pottery suppliers) was mixed to pudding consistency, and poured into the container. Jiggling the container gently helped to fill voids in the mold, and make bubbles rise to the top. Immediately after the plaster has hardened (a half hour is sufficient), the clay is peeled away from the plaster. Any small holes in the mold can be filled with a small repair batch of plaster.

Tip: If the clay used as the master is too dry, some of it may adhere to the plaster. The best way to remove it is to wait until it is bone dry, and then to wash it, although you may be able to remove it quicker with a toothbrush or sponge.

The resulting master can be pressed against a pat of clay. Generally I will press it onto a cloth surface until I think the design is well transferred. Then I will apply clay slip to the back of the impression, and push the clay pat onto the desired pot. If the plaster mold is well dried (on top of the kiln, especially), it will release the clay easily many times. A sprinkling of corn starch may aid release.

Using a clay master works nicely for What-you-see-is-what-you-get projects, except that it is difficult to produce raised lettering with clay masters. That's why we also need to know about:

Plaster Master Stamps In the church commemorative stamp , lettering was provided by carving into the plaster stamp after it had been cast from the clay original. By carving letters into the plaster backwards, the impressed image will result in raised forwards letters.

Tip: This may take a little practice--try writing backwards on a piece of paper, and check your results by looking at it in a mirror.

To make plaster master stamps, you might make a number of small stamp blanks of different shapes. Old film canisters or pill bottles may be the right size. Give them a light coat of petroleum jelly to facilitate releasing from the plaster--but expect to ruin the containers to get the plaster free anyway. Leather hard shapes of clay can be used (easily deformed to oval or squarish shapes) and they will release without any petroleum jelly. Mix the plaster and fill the containers as recommended above. After removing from the mold, take off any sharp projections with a loop tool or knife. Patterns can be drawn on the plaster with pencil or marker. Carving can be done with old dental tools (ask your dentist), a nail, or other sharp objects. It is preferable that they are not too sharp, as the resulting carving will have a sharp edge as well. It unifies the design to carve a trough around the outer edge of the stamp, which will result in a raised edge to end the decoration. Smaller stamps can be pressed into leather hard or fresh clay. Larger ones may need to have a pat of clay forced onto the mold, and to be pressed out on a hard surface (as pictured above) before attempting to transfer the pattern. Stamp patterns can include geometric designs, natural leaves and flowers, signature monograms, family escutcheons, or camp logos. They can be used to make a more unique version of the I (heart) Whatever place mugs...

Throwing RibsRibs, or kidneys (or whatever part of the beast you like to eat), are used to smooth thrown clay surfaces, and to reduce friction while bellying (forcing) out a pottery shape. Most of the ribs I use are made from plastic, and the main source of sturdy plastic is credit cards. Prepaid phone cards are a good source.  Tip: On any usable credit card, make sure you cut off the number, or wear off the magnetic strip, to prevent misuse. No amazing procedures here: Cut with a scissors, and sand if the edge is sharp.

Throwing SticksA throwing stick (Fig. 4) is a rib extended to reach inside vase shapes and belly them out. They can reach in a small top hole, where hands would never fit. With a little water on them, they will stretch a shape far thinner than is possible by hand Another feature of throwing sticks is they will work inside without supporting them simultaneously on the outside. This makes it possible to blow up a slipped decoration similarly to the way printing on a balloon gets larger as it is blown. Making a throwing stick is easy. A rubber ball can be nailed onto a dowel to make a simple version. I prefer the rib part to be thinner, though. The shape can be cut out of 1/2 to one inch wood (hard or soft) with a hand coping saw or electric saber saw. The length varies for intended use, from eight inches to two feet. The handle can be whittled or sanded to smooth the edges, and the rib area should be carved thin at the edge, and sanded smooth. Linseed oil is a good preservative. To use the stick, start by pulling a tall cylinder with a narrow neck. Insert the rib end, and push slowing out where you wish to expand the clay, moving up or down as necessary to expand adjoining areas (See Figure 5).

Tip: Try painting on a decoration on the wet clay with iron oxide or decorating slip. Use only the throwing stick to expand the cylinder, and the decoration will be expanded. Note that colors are thinned in this process, so may be muted when glaze is applied.

Tip#2: You can apply dry powder clay, or clay mixed with oxides to the outside of the cylinder before expanding it. When the stick is applied, the outside surface will become very cracked and ancient looking. A thin glaze (such as C-4 in the appendix) will protect but not obscure the texture.

Sponge on a Stick Okay, it's humble, I admit it, but most potters use these when throwing, to wet the clay or remove excess water. I also use a smaller sponge and stick to reach inside small vase shapes to remove water, and to clean up glaze flecks on wax resist when glazing. (Okay, if you don't want to make one, the small gray foam edge paint sticks sold at hardwares work well for that purpose, too.) I first made my own sponge on a stick when I saw that the commercial ones available at the time used cellulose sponge. Cellulose sponge clogs with clay immediately, and breaks up into globs in no time. The best sponges for cleanup, glaze removal, etc. are the cheap artificial sponges, sometimes sold for washing cars at hardware and variety stores. Buy a bunch of them, because you'll need some to make your sponge on a stick... Worn out artist's paintbrushes make good handles. Doweling (8-10 inches long) works well also, and seems to last well without any preservative. A notch can be cut around the dowel where the sponge is to be tied on, to help secure the sponge. Cut a sponge into pieces two inches long and an inch and a half square. Poke the handle into the two inch part, about half way. Wrap the part with the stick in it with two feet or more of fish line, keeping tension as you go, and leaving six inches at the beginning to tie onto the end piece. Tie several square knots and cut off the excess fish line. Save the extra pieces of sponge for when the other wears out...

Hole PuncherA hole puncher makes holes in clay, usually at the leather hard stage, because it's too sticky earlier. I use hole punchers to make colanders, planters with drainage, and to add two holes on the foot of platters so they can have a loop added for displaying on the wall. The following design may seem a bit odd, but I had it recommended to me years ago, and I think its a great tool. The cutting end is a removable pen nib used in calligraphy, available at art supplies, usually for less than a dollar. Science Surplus currently has them for cheap.  It doesn't matter what size the pen nib is, the functional part for our purposes is the semicylinder which holds the pen nib in the pen holder.

The pen nib is attached to a dowel the right diameter to fit inside the pen end, as shown in figure 6. A short pencil can also be used. It's important to keep the length 4 inches or less, because the hole tool is often used in places where the end might poke the other side, if too long. Apply glue to the end of the dowel (I prefer the thicker Goop (TM) or ShoeGoo (TM) glues). Tie with two feet or more of fish line, leaving some at the beginning to tie with, and applying tension while winding around the nib. To use the tool, poke through the leather hard clay, twist, and remove. The plug of clay tends to be removed with the tool, and the semicyllndrical shape makes it easy to extract the clay bits from the tool.

Tip: Because it's easy to misplace or break tools, buy extra nibs and other harder-to-come-by parts to keep on hand.

Clean Up ScraperWhen it's time to clean off bats, or scrape the clay wedging area, a good scraper makes it all easy. To clean a plywood wedging area, a drywaller's broad spackle putty knife works quickly, and is ready made. For use on the wheel, I prefer a small scraper to scrape the bats while they spin, just before use.

Health Tip: To reduce the hazards of clay dust when cleaning bats, use your sponge and stick to moisten the clay left on the bat before scraping.

To make a comfortable scraper, take a piece of one inch wood about the size of a credit card. Smooth the edges by sanding, planing, or filing. Placing the wood in a vise, make a cut with a hand saw approximately one inch into the wood. (See Figure 7). Insert credit card into the slot. Glue in the card, or drill two holes as shown to hold the card in.

Glaze Thickness Tester:A glaze hydrometer (thickness tester) measures the specific gravity of a glaze, to help standardize the thickness of a glaze from one batch to the next. If you mix your own glazes from recipes or purchased powder, hydrometers can save a lot of misery from glazes too thick or thin. After breaking several $20 glass glaze hydrometers, I invented the following tool which is as accurate as the sealed glass version, but nearly unbreakable. Cut an eight inch piece of half inch doweling. Using a permanent felt-tip marker, mark the side with a centimeter ruler, one mark around for every centimeter, and number them with 1 at the bottom. Seal with polyurethane or shellac (this is important, to prevent marks from becoming illegible, or waterlogging to affect accuracy). When dry, add a small screwy to the bottom center of the dowel (predrilling with a small bit will help prevent splitting). Secure fishing weight to screw eye by tying with fishline or wire. Determine the proper weight by testing in bucket of water. The weight should be sufficient to pull nearly all of the stick under plain water. In the more viscous glaze, the hydrometer will then stick up higher. To use the tester, drop it into a bucket of glaze, and note the number on the stick. The thicker the glaze is, the lower the number will be. Test your current working glazes, and make note of the resulting number on your recipe page. Then test each new batch. Reading the tester to the nearest half is generally as accurate as is needed.

Tip: Wet the hydrometer each time before using. It will slide through the glaze better, and be less likely to have the numbers obscured by the glaze.

Glaze mixing Addendum: Someone wrote asking how to mix glaze with the hydrometer.  A hydrometer is just for standardizing the thickness of glaze from one batch to the next. You need a sieve and something to mix the glaze with, such as the Kitchenmajig at the top of the tips page.  You add water to the glaze in a plastic bucket, until it's about the consistency of half and half.  Then you put it through the glaze sieve several times--80 mesh is the size of the screen.  A suspension agent like Epsom salts (recipe on the tips page) helps prevent settling, but glazes must be stirred frequently when using. 
These instructions are for making glaze for dipping.  It's basically the same if you're brushing it on, only you need to apply about 3 even coats when brushing.  
She wrote back:
how do I know what the hydrometer should read in the very first batch?
Only by trial and error, or preferably some experience working with glazes.   Glazes vary in their effective thicknesses. A transparent matte glaze may be very thin.  Opaque gloss glazes have to be fairly thick to cover the clay. 
Generally the thicker the glaze, the better, but if it's too thick, the glaze will tend to craze (crackle) because it won't fit the clay under it, and it will tend to crack off or pinhole on drying, which may also translate into baldspots or  pinholes on the final pot (this gives you a clue, if you have a thick batch of glaze, to try it on a pot and see if it pinholes, or crazes.  Too thick gloss glaze will also tend to run off the pot.  When you have the thickness of glaze that works the best, that's when to use the hydrometer, so you can repeat it with the next batch (by starting with it too thick, and adding water till the hydrometer reading is correct.)

Wheel Powered Grinding DiskThere are times when something has got to go: Like lids that don't quite fit, especially after warping a bit on the kiln shelf (I know it's never my fault...) Or goblet bottoms that teeter a bit when sitting on a flat surface. A flat mounted grinder can save pots in those situations. Grinders are useful in many forms (See Chapter 3--Tricks of the Trade). But a good controllable grinder can be easily made using the potter's wheel. The idea is simple: go to an auto supply or hardware, and ask for the largest diameter grinding pads they have (up to 10 inches, medium grit is best). These pads are used on high speed grinders for autobody and metal working, but they also work well at lower speeds such as those encountered at your electric--or even kick wheel. Glue the pad onto a bat, secure it to the wheel head, and get it spinning fast. Hold the pot steady on the grinding surface, and keep your hands away from the grinding area. A mask and protective eye wear are advised when using a grinder.

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