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Underglaze, Colored Slips, Compatible?

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I'm wishing I had a few more colors of slip made up for a project I'm working on.  I have several bottles of commercial underglaze in the colors I want.  For applying on leatherhard pieces, can I use the slips as a base color and add underglazes along with and/or on top of, the slips for some accents and detailing?  I plan to do some carving at leather hard, then dry and bisque to 05, then clear glaze.  The slips I have are white clay slaked and sieved, with oxides added. 

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I have never done this but I don't see why it wouldn't work. You would have to wait for your slip to dry out some before you add the moisture of the underglaze. I don't know how deeply it would sink into the slip though so you would have to adapt your carving technique to the layers of color or paint with underglaze again after carving.

 

I would not recommend coloring your slips with underglazes though. They wash out color wise and stay wet longer.

 

I have adapted the Skinner Blend technique to our earthen clays. You can produce a wide range of secondary colors in half an hour which is great for slip users. Google it and just substitute slab roller or rolling pin for pasta machine in the instructions.

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Thanks, Chris, I want to do a multi colored sgraffitto project and have all these under glazes, so hoped I could use them along with the colored slips I have.  The main body of the work will be the slips, with the under glazes supplying small areas.

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I have done the multi colored slip sgraffito and it works really well with slip layers. The effects come through when the layers of color are visible. If you scroll about half way down this page there is an image of a vase.

 

http://ccpottery.com/bio.html

 

The most important thing is to wait until the layer of slip is touch dry before applying the next color. You also have to do the carving at the exact right time ... Do not let it get too dry or it will chip instead of carve.

Please let us know how it works with the added underglaze.

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In my experience ...

 

My colored slips are clay, mason stain, water ... mixed to an almost yogurt like state.

Commercial under glazes have the same ingredients plus some additives and are about the consistency of whipping cream. You can open the lid and let them thicken up, but they still will not act like a slip.

 

Slips will stay on the surface and when dry, still have height.

Under glazes will soak in like paint and are not three dimensional. When applied thickly they are not as pliable as slips.

 

Slips need to be adjusted for different uses ... Floc or defloc.

Under glazes can be used as is on green ware, bisque and fully fired work.

 

I have a section under "clay lessons" on my website where I illustrate various ways to work with slips.

www.ccpottery.com

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Thanks Chris.

There was an item in Ceramics artsdaily newsletter where a potter, Holly?, gave clear instructions on this but I lost the address.

I found her recipe though,

Holly's Underglaze.

Cone 04-10

Ferro Frit 3124        33.3%

EPK Kaolin              33.3%

Commercial Stain    33.3%

Seive 80 mesh, ballmill 12 hrs.

Add Sta Flo LAundry Starch till mix reaches yoghurt stage then sieve again. Goes mouldy but maybe vinegar will help this. Another binder may do the job of the starch.

Some one may know the link.

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As far as I know you should NOT mess with ball milling encapsulated stain because you destroy the protective layer.

As to the other plain Mason stains I can only ask why you would ball mill them??

Of course, I wonder why you would put a day or two of expensive personal labor into manufacturing under glazes ... A product that is done excellently by Amaco for one!

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Yes seems unnecessary unless you are looking for a specific colour. I am interested in the ingredients of underglazes as I have a blue which does not fuse into the glaze but instead cracks and buckles the glaze. I try to make it more fusible by adding some of the glaze wich is going to cover it, but perhaps there is a better addition. Does anyone know?

I agree re ballmilling, a good agitation should suitably blend the ingredients above.

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Frit in an underglaze is a flux that helps the colorants adhere to the surface of the vessel. For example, a mixture of red iron oxide and water, brushed on leatherhard and fired to bisque. You don't get to a high enough temperature to melt the red iron oxide and fuse it to the bisque ware and it can brush off after being fired. Frit will help it melt and adhere. You can use things other that frit, but you do need something to fuse the underglaze. Commercially made underglazes, as well as mason stains, have a frit in them.

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Under glazes usually have a feldspar or other flux, but not enough in my opinion.

 

I would be surprised if Mason stains contained any added flux. Without adding additional flux most Mason stains are quite refractory.

 

The original purpose of Mason is to color cements.  People working in ceramics began to misuse them and Mason found a new market for their existing product.

 

Frit in an underglaze is a flux that helps the colorants adhere to the surface of the vessel. For example, a mixture of red iron oxide and water, brushed on leatherhard and fired to bisque. You don't get to a high enough temperature to melt the red iron oxide and fuse it to the bisque ware and it can brush off after being fired. Frit will help it melt and adhere. You can use things other that frit, but you do need something to fuse the underglaze. Commercially made underglazes, as well as mason stains, have a frit in them.

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Mason Stain has provide me with recipes in making under-glaze, and they're very helpful in creating custom color blends.

 

But I'd be very surprised if Mason Stain passes out recipes to potters for making Mason Stains. Put some piles of Mason stain on a pancake and fire them.  Very few of them are not still free-flowing powders after the kiln firing. They're refractory.

 

The recipe for a White under-glaze was doubtless supplied by Mason Satin as the potter claims, but this does not mean this is Mason's recipe for making 6700-White Mason Stain - which is a mixture of Zirconium, Alumina and Silica melted at temperatures hotter than Cone 10 and reground.  http://www.axner.com/mason-stain-6700.aspx

 

Mason's white is slightly different from Zircopax which is Zirconium and Slica melted at temperatures hotter than Cone 10 and reground. http://digitalfire.com/4sight/material/zircopax_1724.html

 

In a pinch I've used Zircopax as a kiln wash - it's that refractory. No flux.

 

Cement makers have never had a need for flux in their cement colorants.  This is the same product Mason sells to potters.

 

I would be surprise if Mason stains contained any added flux. Without adding additional flux most Mason stains are quite refractory.


http://iweb.tntech.edu/wpitelka/syllabi-handouts/handouts/mason%20base.htm

Mason uses both feldspar and frit.

 

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Absolutely correct. I add gerstley borate because in California it's far cheaper than frit and suspends like clay does.

 

A combination of frit and kaolin will do the same job of adhering the underglaze to the clay in the kiln.

 

ok so for my refractory blue underglaze just whacking in a bit of hte glaze, or a suitable frit should allow more fusing and solve the prob.

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What have I missed? Seems like I remember the supply of gerstley borate was closed down, and folks started using subs for it such as gillespie borate. I have a bag of gerstley from years ago, but checking SC find it is not available from them. Is it available at a decent price out there, or is it best to sub with the gillespie?

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Sit on it , Pres, may fund your bowling pursuits. :)   If the commercial stuff is anything like the commercial Cornish Stone, it may be chemically the same but it is a whole lot hungrier than the real stuff. i.e. glaze not as appealing, to me anyway.

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Jon Brooks bought the Gerstley Borate name when he bought the mine.

 

Laguna Clay Gerstley Borate satisfies all of my needs at a very inexpensive price.  God only knows what he makes it out of now, but I think he does a better Gerstley Borate than the other GB substitutes.  http://www.axner.com/gerstley-borate.aspx

 

Our price delivered from Laguna's City of Industry site is something like $26 for a 50 pound bag.  It's considered a clay, so is eligible for the clay volume discount that ranges from 5% up to 30% depending on how many pounds you order.  500 pounds 21.6%; 1,000 pounds 25% et al.  We're about 35 miles from them.

 

What have I missed? Seems like I remember the supply of gerstley borate was closed down, and folks started using subs for it such as gillespie borate. I have a bag of gerstley from years ago, but checking SC find it is not available from them. Is it available at a decent price out there, or is it best to sub with the gillespie?

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Holly's under glaze  with 33% of a frit, does that make it a glaze?

 

Lots of terms used loosely maybe.. Underglaze usually used on bisqued pot and so needs something to help it stick and fuse to the pot ,fired low then glazed.

Slip,basically clay and colour , but because it is applied to leatherhard, usually, pots it needs altering so that it dries compatibly with the leatherhard clay.

Engobe another animal, slip glaze eeeek.

Now potters add things to make all of that work then along comes someone courting failure  ;) and puts underglaze on raw pots, slips ontop of glaze etc .Don't know what % of fluxes etc moves one of the above from one category to the other, or perhaps it is just how you use it that determines that. Or how vitrifiable it is..

Now some ceramicist can explain all of that in science speak.

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So Gerstley is no longer available? I only had an 80# bag I think. I am going to try tests with the Gillespie, as I have heard that it is pretty close to the Gerstley. That way my glazes should be consistent under the new one. I am not sure if there is another reasonable sub out there without restructuring the entire glaze.

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Here's some actual info on Gillespie v. Gerstley borate:

http://www.sheffield-pottery.com/GILLESPIE-BORATE-10-pounds-p/rmgilbor.htm

Since the Gillespie is manufactured and not mined: it is much more consistent, repeatable  , and dependable:

The Laguana / Gerstley is from a a notoriously highly-variable vein of material. (no it is not from overseas) It can be very different bag to bag.

It's a good idea to switch to Gillespie since it is a blended material that therefore can be consistent batch to batch.

It looks a bit different than Gerstley, but since Gerstley is always different from itself, it is hard to compare.

At this link you'll seem some tests of floating blue that (I believe) Jeff Zamek did to show similarities/differences

 

Again , it is worth considering switching to the more consistent material, it takes a lot of headaches out of troubleshooting. If you use Gerstley, you should buy full bag, and do line blends to test. Then next time you need a bag, you should line blend again.

This is not necessary with the Gillespie stuff since it is going to be the same from bag to bag..

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That's Laguna Borate, Norm, not gerstley borate. !!!

The Laguna borate is a sub like the gillespie borate is.

 

By the way there are tons and tons of the actual Gerstley borate kicking around so it is important for people to migrate to the gillespie or the laguna borate as apparently you have wisely done.

But you are going to confuse people when you keep calling the Laguna borate, gerstley borate.

If you call a ceramic supplier and order Gerstley Borate you will get Gestley Borate.

We have many ton's of it here.

We also stock the Laguna borate and the Gillespie.

Reports from most folks so the Gillespie is the better of the two subs but either is better than the original.

Neil has a nice bit on why actual gerstley is not good http://neilestrickgallery.blogspot.com/2011/03/gerstley-borate.html

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