Comment

Comment by Marla Stroup on March 12, 2014 at 7:19pm

Tyler, great idea, thanks, the MSDS sounds like what I need. I'm looking for strength after it is fired. It would be cool to have small wisps  of clay here and there or possibly for making jewelry.

Comment by Norm Stuart on March 12, 2014 at 3:24pm

If you mix vinegar with sodium silicate, you obtain "silicic acid" which is a gel of microfine silica (quartz) and sodium acetate. Sodium acetate is the flavoring ingredient E262 in "salt and vinegar" potato chips.

Silica Gel from sodium silicate and vinegar

People with electric kilns buy "silicic acid" as "brick hardener" which is applied to kiln brick then fired to produce a hard silica surface on soft fire-brick.

Comment by Norm Stuart on March 12, 2014 at 3:01pm

The resistance to glaze, caused by the glass formed by sodium silicate, is the primary reason I use Darvan rather than sodium silicate and sodium carbonate in slip.

We use Darvan 811 which is compatible with iron containing brown clay.  Darvan 7 is used for white clay.

Darvan 811    Darvan 7

Darvan polymers are added to drinking water to remove suspended clay, and any other particles like virus and bacteria.  The deflocculated "flocs" of Darvan attached to particles are then filtered out in sand beds.

This is a photo of the mixing tank which adds Darvan to the drinking water for the City of Los Angeles, piped in from the Colorado River. 

It takes 12 hours or so for the Darvan to attach to all available particles in the water before filtration through sand beds.

The Darvan polymer strands with attached particles and captured by back-flushing the sand beds and sent to a solid waste dump.  When used in ceramics, Darvan burns out as carbon dioxide in the kiln.

Comment by Tyler Miller on March 12, 2014 at 12:31pm

Marla, are you looking for strength in your gauze-slip material while it's green or after it's fired?  In my experience the two tend to be mutually exclusive.

Do you have the MSDS for sodium silicate?  It's always a good idea to review material data safety sheets before purchasing any chemical you're not familiar with.  Sodium silicate is no more dangerous than household bleach, but it would be a good idea to learn how to handle it, if you haven't already.

Comment by Marla Stroup on March 12, 2014 at 10:45am

I am also not happy using the sodium silicate just because it seems like a dangerous chemical. I just viewed the link in the article I posted below where the potter uses a small amount of toilet paper, white vinegar (no water at all) and bone dry clay to make a joining slip. This sounds good to me for joining but I'm still hoping to find some way to strengthen my gauze slip material.

Comment by George Lewter on March 12, 2014 at 10:30am

For about the last year and a half, I have mainly used a mixture of 1/2 white vinegar and 1/2 water to attach handles. With a bit of scoring, it works as well as scoring and slipping for me with little or no cleanup of the joint afterward.

I'm hesitant to use magic water because the sodium silicate could potentially seal the clay to some extent and cause a difference in the amount of glaze that area would take up compared to the rest of the piece. Has anyone noticed anything like that happening, or is the small amount of sodium silicate in the water too little to have any effect?

Comment by Marla Stroup on March 12, 2014 at 10:25am

Here's a pretty good article about magic water etc.

http://flyeschool.com/content/two-rules-joining-clay

Comment by Marla Stroup on March 12, 2014 at 10:23am

What I would like to discover (and thought perhaps magic water would be it) is a clay mixture that would be very hard and durable when dry. I'm looking for something that can be used for strength. I've been making slip from dry clay and water with a little vinegar added (1/3 cup per blender batch), then dipping gauze in it and draping the gauze/slip here and there sometimes using it as a bonding mechanism in joints, joining two bone dry pieces.

Here are a couple of candle holders for small votive type candles that give an idea of how I use the gauze slip.

The second photo shows the g/s method as a base or pedestal sort of arrangement. It is for this use that I'm looking for a strong slip mixture.

Surprisingly, I experimented with the magic water to make a slip, dipped gauze in it and it did not adhere to either a bisque fired piece or to a piece of greenware. I mean it basically seemed to seal off from both pieces so that won't work for my purposes.

Comment by Norm Stuart on March 11, 2014 at 8:49pm

Slip made with either Darvan or Sodium Silicate/Sodium Carbonate can become fluid like casting slip if too much water is added.  In the framework of casting the excess water is quickly removed by the plaster mold and the slip gels.

I think deflocculated slip used for slab construction or similar uses should contain far less water. In addition to 0.5% Darvan I add 2% bentonite and 2% Custer Feldspar to the clay slip.  The final feel is greasy and can be used to strongly adhere clay slabs without scoring.

The combination of the bentonite and deflocculant provides better packing and thus better attachment of the clay particles.  The feldspar or the sodium in sodium silicate provides flux in the kiln to better attach these joins.

When flocculating glaze or slip with Calcium Chloride or Magnesium Sulfate you can add more water, but when deflocculating you can't always easily remove the excess water so you have to use less initially.

Comment by Marla Stroup on March 11, 2014 at 6:17pm

Has anyone had experiences with slip made with magic water? I'm experimenting with a batch of slip I just made with magic water. It is quite strange. It reminds me of mixing water with cornstarch. It sets up into a heavy jelly like consistency and then when disturbed or stirred it gets quite thin again. I blew up some small balloons and draped some gauze saturated with this mixture over them. Did a good job of cleaning all my tools etc. since I read that this stuff really sets up hard when dry. I'd be interested to hear other uses if anyone's got stories about magic water, thanks.

Comment by Carl Ray Crutchfield on February 5, 2013 at 1:52pm

redirect me if need be, I am looking for information on using Darvan 7 to create a joining slip to be used in attaching handles.  thanks - carl

Comment by Donna Ferrara on March 20, 2012 at 3:57am

I've been looking  for a cone 6 white stoneware clay body that fires in oxidation to the greyish -white color that white stoneware fires to in a reduction firing.... anyone have any experience with  a white clay body that mimics reduction firing?

Comment by George Lewter on March 15, 2012 at 1:14pm

There is a discussion topic on this http://cone6pots.ning.com/forum/topics/is-it-possible-to-repair?com...

Comment by Joan Scott on February 9, 2012 at 9:44am

I have found a good place for recommended respiratiors if anyone is interested at http://ceramicartsdaily.org/uncategorized/respirators-for-potters/

Any other ideas please let me know. Thanks

Comment by Joan Scott on February 8, 2012 at 11:33pm

Does anyone have the name of a good dust mask to protect during glaze mixing etc., I find the one I have isn't sufficient and is extremely uncomfortable.

Comment by Jan Wallace on August 3, 2011 at 2:54pm

I have recently started putting some paper pulp made from toilet paper in my joining slip. Since then, i have never had a crack in anything that I join. I simply wiz up the tiolet paper in a blender with water and a few drops of bleach (stops it getting smelly in time). Then add approx one tenth pulp by volume to some wheel slops/slip and mix well. I just keep the extra paper pulp/water mix in a sealed container for future use. As it has the bleachin it, it keeps well.

Comment by George Lewter on June 17, 2011 at 12:29pm

Pauline Perdum says, "I use silly putty to mask areas I don't want covered in glaze I plan to dip, don't like to use wax because I invariably get drops where I don't want them.  The silly putty can be pushed over comlex sprigs/texture, etc. then pulled off, washed and put back in little egg to use over and over again.

Works great for bits I want to be unglazed, or glazed after dipping in a different glaze."

Comment by George Lewter on December 15, 2010 at 3:54pm

Vinegar water makes a great clay bonding agent. 

• 1 part white vinegar to 2 parts water.

Paint a little on the surfaces to be joined and mush the parts together.  No need for scoring and slipping the joint.  I've used this on my last 3 batches of mugs, and have only had one handle break loose on drying or firing.