New Mexico Clay’s 2016 Open House, Demos and Classes

April 14, 15, 16       9am to 5:30pm

Call to sign up to reserve your spot

Grace Cooper – Mayco Glazes– Friday morning workshop

12 people in the class, class featuring the Mayco Stencils, Silk screens, Stroke & Coats and Sculpting Media.   Class from 10-12

Diana Faris – AMACO pottery equipment and glazes– Make and take throughout the 3 days

Make and take – Using Velvets and self made stencils to layer images on tile.

Th and Sat 10:30, 12:30, 2:30, 4:30   Friday 2:30 and 4:30

Arlene Smith – Duncan Ceramic– Make and take

Demonstration/talk and make and take focusing on the Color Burst Crystals

Thursday and Sat 9:30, 11:30, 1:30 and 3:30   Friday 1:30 and 3:30

Karen Wise– Shimpo Wheels and pottery equipment– Being her usual welcoming self, demos, throwing, carving and such.

Also Donna’s Truckload of used molds sale!

Sunmolds used and new molds on sale!

Skutt, Olympic and Paragon Kilns on sale 20%

Xiem tools 20%

Kemper 20%,   
DUNCAN MAYCO 20% off,

Pugged Clay 32% off the one lb price, 40% off  2000+ lbs!

Duncan Lusters 40% off.

Clear lowfire glaze gallons 40% off

Many more items too long to list.

Most cone 6 glazes 20% off!

Smooth On 10% off!

Chemicals, Clay ingredients, Slip, too low a price to discount.

Look for our Pallet of old random dry glazes and clay materials.

Rumors Swirl over Custer Feldspar

Janine Gould of Pacer Feldspar reports that they had lost one of their 3 large, 12 foot wide ball mills, the repairs are very expensive. So they will only make 325 mesh Custer feldspar in the future. Also they are not taking any new orders until August and are running 24-7 on the two remaining mills. NMCLAY uses 200 mesh Custer and has for 30 years. WE have plenty for now.

You should be prepared to test your glazes for the finer product, I expect you will see very little change. click here for data sheet

Feldspars in the News.

Imrys has announced the G200-HP mine is run out! I expect Laguna will not be able to make G200-old anymore.

There will be some substitutes from Spain called G200-EU with less potash, but expect to pay a higher price.

We are down to our last few lbs. as desperate potters cleaned us out.

Read all about it HERE

ALSO!

Pacer Custer Feldspar has been accused of not providing the correct ratio of potash and sodium. Rob Roy has published an article in Ceramics Monthly detailing the problems.

ABOUT CLAY AND GLAZE FIT

By Martin Butt of Coyote Glazes

Not all glazes will fit well on all clay bodies (nor do all clay bodies fit well with all glazes), so it is always a good idea to test a glaze on the clay you are using to insure they are compatible. Most of the Coyote glazes have fairly average expansion rates, and are likely to fit most average clay bodies. We have one series of low expansion glazes that can shiver if used on a high expansion clay body, so care should be taken to make sure these glazes fit the clay you are using. They are: Archie's Base, Blue Purple, Eggplant, Gun Metal Green, Ice Blue, Opal, Red Gold and Rhubarb. We have had reports of this series shivering on the following clay bodies: Standard #112, #201 and #245: Highwater Loafer's Glory and Brownstone: Axner's Mike's Stoneware: New Mexico Clay's WH8: Alligator Clay's MC360 Lovestone high fire: Continental's Mid-Range White and Mid-Range Oxidation Body. If you know of any others please let us know. Also if you would tell us the bodies you use that work well with these glazes we can start a list of those too. If the clay you are using doesn't fit with these glazes but you want to keep using them (they are beautiful), the only solution is to try a different clay body. These glazes work fine with most clays, only bodies with unusually high expansion cause a problem.

More about Clay and Glaze Compatibility

Each clay and glaze have their own expansion (and contraction) rate, and if they are too different problems can result. At about 1000 degrees F. the glaze solidifies, and the clay and the glaze undergo contraction side by side.

The most common fit problem is crazing, caused by the glaze contracting more than the clay body on cooling. This means the glaze is stretched over the clay, resulting in a crazing or crackle pattern. Although there is some evidence that crazed glazes may result in a weaker finished pot, the main concern is aesthetic, and many people just ignore it.

Of much more concern is the opposite problem of shivering. In this case the glaze contracts less on cooling than the clay body, putting the glaze under compression. Some compression can be a good thing, resulting in a stronger pot, but too much can cause the glaze to flake off the pot (shivering). In extreme cases this condition can cause the pot to break (shattering). It is important to realize that this might not happen for days or even weeks after work comes out of the kiln, so do your testing early.

Expansion/contraction is often confused with firing shrinkage, which is irreversible. Expansion is temperature dependant and occurs with each heating and cooling. Shrinkage doesn't tell you anything about the expansion rate. Some high shrinkage clays have a low expansion rate and vice versa.

Brant says..... Exactly! Don't use that clay with those glazes or Laguna's beautiful crackle glazes. And while you are at it don't use WH8 for crystal glazes as it inhibits the crystal growth. And don't use a Geil Brand kiln on high iron bodies, just asking for trouble.

Custer Feldspar Chips

Custer Feldspar Chips

Chips of Custer Feldspar, added to clay at cone 10 they gush out and look like this.

Shigaraki Ware


Recognized as one of Japan's six old kilns, the history of Shigaraki ware dates back some 1,200 years to the Nara period (710-794).

There are three points to look for when judging the color of a wood-fired, ash-glaze Shigaraki pot -- the overall color, the glass beads and dribbles formed when the heat in the kiln melts particles of feldspar in the clay, and the scorches that come when the pot is blackened by ash.

Cool!

To order click HERE

New Mexico Clay’s Cone 10 Bodies
for General use in reduction, wood or soda firing.

	ANN’S (NEW) SODA AND WOOD FIRED WHITE STONEWARE:  Our Cone 10 soda and flashing body contains 2 Kaolins (Helmers is one) for whiteness, and stoneware and sagger clays for flashing, also has 10% fine grog. A creamy color in oxidation, a grey color in light reduction. Flashes rust in soda. Throwing notes: “Throws great for tall thin pieces, not a “tight” body” “Throws Like a dream!”
	SOL: All California fireclays give this versatile clay body a pleasing sunny California toasty warm color in reduction. Our sand doesn’t pop out giving the body a smooth texture after firing. Throwing notes: “Another great body for tall thin pieces, moves easily. ”
Rev:12/09/2011	HIGH HILLS II: Our version of the popular Missouri fireclay, Goldart, ball clay and grog type stoneware. Very forgiving and throwable clay for production potteries. Tan to gray brown in reduction, medium texture. Jeff Zamik  approved ZAM body. Throwing notes: “It is a “tight” body (it resists your effort to move it). Stands well on its own. Great for wide bowls. New Mexico Clay 3300 Girard NE Albuquerque New Mexico 87107 USA Fax 505-881-6067     800-781-2529  www.nmclay.com

More Materials bite the dust!

No more PV clay. Plastic Vitrox was mined in California, but lack of demand and quality control have doomed the material.

No More Cornwall stone, we have been selling the substitute but its not the same.

Kona F4 now use Minex (good sub!)

White Talc the talc is now charcoal grey.

G200 is being blended by laguna so we still have it available.

Recently New Mexico Clay Customers had a problem with a clay body (High Hills) we have been making for 14 years.

HIGH HILLS is our version of the popular Missouri fireclay goldart ball clay and grog type stoneware. It is a very forgiving and throwable clay for production potteries. Tan to gray-brown in reduction, medium texture.

Cone 10 Shrinkage: 14% Absorption: 0.1%   Penetrometers: 7

We previously had to fix a problem with iron or manganese spots caused by the fire clay Hawthorn 35. This clay is used by various companies to make refractories, cement kilns and other industrial processes. Only 1% is used to make clay for potters. The spots were caused by the fact that the fire clay was unscreened. The purpose of a fire clay in a clay body is to provide tooth or texture.

We are now using a screened (40 mesh) Hawthorn.

The new problem mainly effected people who fire in gas kilns and do a heavy body reduction. These Potters experienced shivering and dunting; probably caused by a change in the chemistry of the fireclay.

The samples the potters brought in showed signs of Black Coring caused by over reducing iron; changing red Iron oxide to black iron oxide or worse-iron silicate. Large amounts of coal and other organics in the clays can exacerbate black coring, so I checked the raw materials for excessive Loss on Ignition.

Everything seemed perfect no problems, L.O.I. was lower than expected for all the clays.

Test of raw clays in High Hills
	Initial weight	Dry*	loss	Fired#	LOI	color
OH #5	294	293.1	0.31%	265.5	9.4%	creamy white
Goldart	294	290	1.36%	263	9.3%	creamy white
OM4	294	291	1.02%	263.4	9.5%	creamy white
Hawthorn 40	294	288.5	1.87%	257.3	10.8%	peach
	grams
	*Bake at 350F for 4 hours
	#Bake at 1000C hold 1 hour 1832F

Large amounts of iron also cause black coring but as you can tell from the clay descriptions this is a light colored clay body.

James Jarrett of Imerys (A Giant Clay Company) took pity on our plight and ran some tests on all the ingredients and the finished clay body.

						New Mexico Clay
						2011-19
Sample id					OM #4	Goldart	# 5	Hawthorn	High Hills
					K-T Clay		OHCC	Fireclay	C 10
								40 mesh	12/29/10
	Received				05/31/11	05/31/11	05/31/11	05/31/11	05/31/11
Chemical
	Si2O3			%	59.3	56.0	59.1	54.1	57.7
	Al2O3				27.8	29.8	27.7	31.2	29.3
	Fe2O3				1.19	1.26	0.83	1.93	1.64
	TiO2				1.81	1.46	2.25	1.37	1.34
	CaO				0.14	0.37	0.12	0.32	0.33
	MgO				0.19	0.49	0.13	0.30	0.33
	K2O				0.45	1.44	0.52	0.96	1.15
	Na2O				0.11	0.11	0.11	0.11	0.11
	L.O.I.				9.2	9.9	9.2	10.5	8.2
	Carbon				0.186	0.102	0.057	0.048	0.085

 This showed nothing wrong.

High Hills clay Reduced
 in Miya Pottery’s Giel kiln at 7000’

Same piece on edge Note the Obvious black core.


EDGE        Glaze      Air


Nothing wrong… So I called a ceramic engineer, Jeff Zamek.

Jeff agreed to try to figure out the problem, he studied the formula and interviewed the people who had problems.

He suggested a few changes in the clay body; we have made these changes and now call the clay High Hills II

My conclusion is that having too much fireclay in the formula coupled with long reducing firing allowed for excessive Cristobalite production. Cristobalite changes its shape around 200°C (392°F). This can cause dunting and shivering.

Some of these steps can help. (this from Laguna Clay)

1. Fire slowly enough 1290° to 1650° F to give the carbon and sulfur in the body time to combine with oxygen and work its way out of the clay body. The burnout process must be done slowly and completely before the glaze begins to melt. In oxidizing atmosphere!2. Provide an oxygen rich atmosphere. In electric kilns, use plenty of ventilation in the bisque fire. If your kilns are densely loaded, use a downdraft kiln vent. In gas kilns, keep the kiln in oxidation from 1290° to 1650° F.
3. When using iron-bearing clay bodies, fire up to 2100° F in complete oxidation to allow for proper and complete burn-out of the organics; then, if desired, begin the reduction process.

Further reading:

Putting the Fire in Clay by Jeff Zamek
http://www.ceramicindustry.com/Articles/Feature_Article/BNP_GUID_9-5-2006_A_10000000000000159771

How to Solve the Problems of Body Cracking and Glaze Popping in Stoneware Bodies  by Maynard P. Bauleke  see..
http://www.kgs.ku.edu/Publications/Bulletins/211_4/bauleke.html