Where to purchase a hydrometer for checking the thickness of your glazes and slips:
The 6 inch hydrometer for smaller buckets of glaze and slip (5 - 10 lbs of dry glaze with water added): Part # 34640-207
The 11 inch hydrometer for larger amounts of glaze and slip: Part # 34640-003
The best way to get good, consistent results with your glazes and slips is to check the thickness in the container before you apply your glaze or slip.
When I add water to a dry glaze I put on an OSHA approved mask for dust particles and I add water in a well ventilated area. Place the dry material in a good sized bucket and start adding water and mixing with your hand. Add enough water to be able to freely move the dry material around. But, not too much water. It's better to add less water to start with and add water as you go.
I like to then use an Immersion Blender. (I have a small one from the cooking section at Target). Blend your dry glaze material with the water until it has a fairly even consistency. Add a bit of water as you go so it moves but it's still a bit thick.
On smaller batches (5 lbs.) I then like to use a Bowl Screen with an 80 mesh screen. I push the material thru with my hand. Or, you can use a Talisman Mixer. Screen your glaze or slip twice thru an 80 mesh screen. Some of the glazes and slips I sell are better screened thru a 60 mesh screen (The Black Magic Slip). Or, not screened at all. (We don't screen the Ash Glaze). I place a recommendation for screening instructions on each slip and glaze.
Gently place your Hydrometer (weighted side down) into the slip or glaze. Let it sink gently into the material. When it stops moving it has "rested" at the scale of thickness of the glaze. Gently pull the hydrometer out of the material and read the number on the side of the hydrometer where the material stopped at. This is your number reading. So, if my recommendation for a glaze is 52 - you would want your glaze to rest at the 52 mark on the side scale of the hydrometer. If it's at 55 - add a little bit more water. If it's at 50, there's too much water. Let it sit over night, skim water off of the top and check it again.
It's good to mix a glaze with water (at least) one day before your going to glaze your work. It's good to let all of your particles hydrate. Some glazes (Turquoise Bubble) have Yellow Iron Oxide. Yellow Iron Oxide can take up to a month to breakdown and hydrate into the glaze. Until then, you have lots of yellow spots.
*Important Note about Bisque Firing Temperatures:
The Best "Interface" layer between the Glaze and the Clay body: can only happen if the clay body is still slightly porous after it's been bisque fired. This way the glaze can penetrate the clay body and create and Interface layer.
To bisque fire a clay body too high closes off the clay body and the glaze will "sit" on top of the clay like a layer of paint. Over time moisture accumulates between this layer and the glaze could pop off of the surface of the clay body. We want the clay body and the glaze to actually melt into one another and weld together. For porcelain - it's only necessary to bisque fire to cone 08. Porcelain is clean and free of dirty, organic material. It doesn't need to be fired any higher. Porcelain with celadon or translucent glaze has an incredible visual depth to the surface. This is partly due to the fact that Coleman Porcelain is over made up of more than 50% glass.
A porcelainious stoneware (like B-Mix) is still somewhat clean. You can bisque fire it to cone 07. Other (more groggy) stonewares will need to be bisque fired hotter. Try cone 06 to start with.
The Best Spray Gun for spraying slips and glazes is sold by Northern Tools. It's a Green Spray Gun: https://www.northerntool.com/shop/tools/product_200319459_200319459
Tom Coleman is a mid-century fine art potter. For more information about Tom and Elaine's work visit: http://tomandelainecolemangallery.com
Scroll down to read information about the following slips and glazes:
Amy's Magic Slip
Black Slip Glaze
Diamond Black Slip
Cone 10 Reduction and Oxidation Glazes
Mesquite Ash Applications
Amy's Magic Slip
arrives at your studio as a dry material. This way you can also add your own colorants, oxides and stains to the slip mixture if you enjoy experimenting with colored slips.
Important Note: Be sure to keep your slip covered tightly with a lid whenever you're not using it.
To Mix the Thickest Decorating Slip add water and mix it like it's thick mud. I then push/force it thru a 60 mesh bowl screen twice. Be sure not to whip the slip around with an electric mixer and fold air bubbles into it. Simply let it fall from the screen into a clean bucket.
Thick Slip Application When the slip is mixed to a thicker consistency you can apply it to wet work with a brush, tools, your hands, etc. When the slip is thick it's best to apply it right after you've thrown and ribbed the form. I spread it on with my hands (while the wheel is spinning) like it's frosting. Then, I like to use the larger Red Rubber Rib made by Mud Tools to gently even out the surface of the thick slip while the wheel is turning. Then, I use different Slip-Tools to create marks and patterns. Amy Kline's facebook page has demos for application and decorating.
To Mix a Medium (thickness) Slip for decorating on work that's leather hard. You'll add a little more water than you did to the thickest slip. Be sure to screen the wet slip 2 times thru an 80 mesh screen. Please refer to the directions above for more details on first mixing the slip. For a medium thickness add water until the slip falls from the brush in a thick drizzle.
To Mix a Thinner Slip (for Spraying Slip): Add a little more water than the applications above so the consistency of the slip is to 50 on a hydrometer. Be sure to screen the wet slip 2 times thru an 80 mesh screen.
Spray Application of Thinner Slip: Geil Kilns sells the best spray gun on the market for spraying on slips and glazes. Or, you can purchase the spray guns through Northern Tools online. Look for the green one with a 2.3 mm orafice. Spray apply thinner slip onto bone dry work. 3 rotation sprays is plenty. You may need to let the slip set up a little between coats. For more instruction on spray application you can attend any of Tom Colemans hands-on workshops around the country.
Adding Color to Magic Slip: You can take this slip in it's dry mixed state and weigh it on a gram scale and add your own oxides and mason stains to it. For example: Take a 1000 gr. batch of Tom's white decorating slip and add 100 gr. of any mason stain to it. This equals 10%. I arrive at this amount by doing the following calculations: 1000 x 10% = 100. Some stains, carbonates and oxides are stronger than others. Email email@example.com if you would like more information.
Colored Slip Mixing and Application instructions are the same as the information for Magic Slip listed above.
Mixing Directions Add water so the consistency of the slip is to 50 on a hydrometer. Screen once thru a 60 mesh screen.
Application Directions: Spray at least 3 full rotation sprays of this slip glaze to be sure you have a good application.
This Black Slip-Glaze can be applied and fired in several ways:
1) Black Slip-Glaze can be dipped or sprayed onto leather hard or bone dry work and then bisque-fired on. If the slip shows lots of cracks in the surface when it's dry it might be too thick of an application. I like to use a piece of test-bisque to check the thickness before I use a glaze on my work. We recommend bisque firing the black slip glaze on if you plan to put any other glazes on top of it.
2) Black Slip-Glaze can be sprayed or dipped onto greenware and once fired to cone 10. Just make sure it's completely dry before bringing the kiln up in temperature.
Please test carefully and take note that there is already some "flux" to this slip-glaze. Place onto an extra piece of shelf or cookie in case your glaze test runs.
Crystal Tenmoku (CT Oil Bloom)
Mixing Directions Add water so the consistency is at about 55-58 on a hydrometer. (You want the consistency of the glaze to be a bit thicker than a normal glaze). It may need to be a little thicker than 58. Screen twice through an 80 mesh screen. A cap-full of muratic acid into the glaze when you're stirring will help to keep your particles suspended.
Application Directions Tom has been spraying the Crystal Tenmoku on thick. Since the glaze is mixed up as a thicker consistency - try spraying about 3 rotations. Add a 4th if it looks like it can go a bit thicker. We'll be dipping the Crystal Tenmoku in our next firing toward the end of April. We will be sure to post our results.
Mixing, Application and Firing Directions for any of our Cone 10 Reduction Glazes:
Add water so the consistency is somewhat like mud. Then, screen this glaze 2 times thru an 80 mesh screen. Then, add water to the glaze until it reads 50 of the hydrometer scale. Spray apply about 2-3 rotation sprays to make sure you have a good application of this glaze.
Kline Crystal Glaze-Oxidation Cone 10
This glaze develops hundreds of beautiful crystals in the following colors of glaze: Turquoise, Midnight Blue, Brilliant Blue and White.
Important Note: Apply this glaze to porcelain that's been bisque fired no hotter then cone 010. If you're applying it to stoneware you'll want to bisque no hotter then cone 08.
Mixing directions for Kline Crystal Glaze-Oxidation Cone 10: Add water so the glaze is the consistency of mud. Screen 2 times through an 80 mesh screen. It's important to screen the extra black carbon out. This material is originally screened through a 100 mesh screen. But, when water is added - some of the particles "fatten up" and need to be screened out. Mix this glaze to a 50 on a hydrometer.
Application instructions This glaze can be dipped or sprayed. Do your own tests and notes for consistent results.
There's no special firing schedule required. Fire the kiln to cone 10 for the cone 10 formula. All kilns fire differently. To see how your kiln is firing it's best to place large, self-supporting cones in different places around the kiln.
Mesquite Ash Applications: Mesquite Ash can be applied as a dry ash sprinkled from a shaker over glazes before being high-fired. It works great over some Shino Glazes. And, it can produce beautiful colored areas when applied to other glazes. Mesquite Ash can also be added directly to a glaze base formula. Start with an addition of 10% Mesquite Ash, fire to cone 10 reduction or oxidation, and adjust the amount added after seeing your results. Be sure to keep notes as you test. Mesquite Ash is a flux and (possibly) a crystal former.
Kline Crystal-Reduction Glaze
Our formulation of this glaze (which was originally created by Mitzu Yanagihara) produces beautiful micro-crystals in some kilns. It's very sensitive to forming extra color (flashing) from other glazes around it in the kiln giving it a natural opalescent quality. This glaze works best fired in a gas kiln to cone 11 with good reduction. And, it works best in a brick kiln. We recommend at least 8 hours of firing from the time reduction starts to the end of the firing to make sure you get a good soak for the crystals to form.
Mixing Directions for Kline Crystal Glaze-Reduction: Add water and screen 2 times thru an 80 mesh screen. You will want the water content to register 47 on a hydrometer scale. This glaze likes to settle out very quickly. You will need to (carefully) add a cap-full of muratic pool acid to this glaze immediately after screening it to make sure the particles stay suspended. Add the cap-full of muratic acid and keep stirring with a metal spoon for a few minutes. Let this glaze sit overnight and re-screen and add a little more muratic acid before using.
Please take precautions and wear gloves and eye protection while using muratic acid. If it splashes onto your skin wash it off with water immediately.
Kline Crystal Glaze Application: This glaze is best if sprayed about 3-4 rotation sprays. It can also be dipped. We've gotten the best results when applied over the Black Slip (sold on our website). This glaze has to be fired to cone 11 reduction. It likes to have a soaking heat from other pots around it. And, it fires best in a brick kiln.
Special Note: Our Slips, Mesquite Ash, and Glazes are also available for purchase at Tom Coleman Workshops given at Geil Kilns in Huntington Beach, Ca. And, in Las Vegas, NV.