Issues with Jen's Juicy Fruit - Only problem glaze in a full load of tests?????

I would appreciate some feedback re this Jens Juicy fruit glaze I tested the other day. I fired a kiln load of tests with success EXCEPT for this one glaze.

Recipe I used

Neph Syenite     49

Silica                12

Whiting             11

EPK                  10

Gerstley Borate    9

Lithium               9

Add:

Red Iron Oxide   4.0

Rutile               6.0

Soda Ash         10.0

It has blistered where thicker (in the deeper texture lines you see and underside of the test ring) and I can pop the blisters to expose the perfect glaze underneath. I had one on the top shelf and one on the bottom which is usually cooler with the same outcome.

I fired the kiln to a flat cone 6, as i soaked at just under 1200 for about 1/2 hr. Kiln naturally cooled to 900c, at which time I turned back on a held for about 1 hr.

Could the blisters be due to overfiring or perhaps due to thickness of applicatoin. Just confusing as other that the areas of blisters, the glaze looks great and how I would expect it to turn out?

Thanks in advance. Jan

Views: 3215

Reply to This

Replies to This Discussion

Hi Jan,

I'm trying to trouble shoot the same recipe. I don't have blistering, but I have some crawling and a lot of pin holes and small crater like holes.

The most common reason for blistering is an overly thick application of glaze. Firing too hot or too quickly at the end of the cycle can also contribute to glazes blistering. I would try soaking it at the top temperature for a half hour before cooling to resolve the blistering.

I've also read that soda ash can produce large amounts of out-gassing.

The next time I use this glaze, I am going to try soaking it at 1800F to see if I can develop some more color. It came out very dull and muddy on my test tile, but I tried it on a pot anyway with some interesting results. I like it except for the trouble spots. I'll let you know how that goes.

Jen

Attachments:

Hi Jen, Thanks for your comments. I agree with what you have said and I think that for my results above, my glaze application was a little too thick. I have come to this conclusion as the glaze only blistered in the deeper lines on the tile where the glaze was thicker as the thinner area came out fine where. Perhaps your glaze results are a result of application of glaze and thickness too? The trials and tribulations of glazing. Sometimes very frustrating and other times a joy.

John Post has very interesting remarks about firing Jen's...

Also one may question the accuracy of the pyrometer reading.  I have used 2 in one firing as insurance.

Several glazes use soda ash, and I'm not sure why.

The following is copied from Tony Hansen's Ceramic Materials Database:

"Sodium Carbonate
The most common form of sodium carbonate
Formula: Na2CO3 or Na2O.CO2

Chemistry %
Na2O 58.70

Volatiles %
CO2 41.30
DENS - Density (Specific Gravity) 1.44
MLPT - Melting Point (MP) 34C D
In ceramics, a common use of soda ash is as a soluble deflocculant in ceramic slips and glazes. It works well in combination with sodium silicate to produce slips that do not gel too quickly and whose rheology can be adjusted for changes in the hardness of the water. Higher soda ash in proportion to sodium silicate will produce a slip that gives a softer cast (stays wet longer). The total soda ash and sodium silicate amount should be tuned to create a slip that will eventually gel if left to stand. This thixotropic behavior will prevent it from settling.

Sodium carbonate is the preferred deflocculant for thinning glaze slurries.

Soda ash is not normally used as a source of Na2O in glazes because it is soluble. It is used as a source of sodium in frits and glass. Its solubility makes it an ideal flux for Egyptian paste glazes."

I speculate that the blistering is CO2 from the soda ash that absorbed into the clay body. As the temperature goes up the soda ash breaks down into Na2O and releases CO2 gas that builds up and tries to escape to the atmosphere, creating bubbles if trapped in the liquid phase glaze. Perhaps the blistering is an unwanted side effect of trying make to the glaze slurry easier to store or to apply?

It would be interesting to create an equivalent glaze sourcing Na2O from non water soluble material. 

I have a same problem drive me insane. a lots of place saying that temp should be high and hold a while fro soak. do you have any idea for firing schedule?

I seem to recall this same problem when using it by itself.  When layered with other glaze, it usually behaved.  I had 2 different formulations.  One was from Glazemixer & the other one I mixed myself.  I don't know if they were identical, but they both had issues.  When I do some more Stephen Hill glazing, I think I will try Norms revision & see how it behaves. When I used it in ^10R at the art center, there were less problems.  jhp

May I suggest Jen's Juicy Fruit - Revised

I've never been happy with the original, so I've made a version without soluble ingredients.

The Insight chemistry looks somewhat different only because Digitalfire does not use the current chemistry for Gertley Borate.  I could remake my version to match the old version if you had used old gertley borate.

Here are some pics of pots using JJF.  The 2  are layered with other glazes, while the one with handles is mostly JJF by itself.  It's not too pretty IMHO. These were done in a ^10R firing 3-4 years ago.  I also think one of them has JJF with extra black iron, but I don't know which.  jhp

This version of Jen's Juicy Fruit with Spodumene relies on less lithium carbonate which tends to fall out of suspension.  Fewer decimals too.

I quite like JJF, I've not used it much as yet but intend to continue with it.

My only problem so far has been crazing, everything I've glazed with it so far has crazed.

This mug is probably the worst example and the other pot is the least crazed, it's hard to see it, but it is crazed.


Edit:a misunderstanding with the image posting - but they are both there eventually - albeit in two posts. ;)

Reply to Discussion

RSS

Videos

  • Add Videos
  • View All

Use These Links to Support Us

Low cost flat lapping disc can be used on you potters wheel if you, drill bat pin holes in it, and provide a trickle of water to cool it. At amazon.com, 120 grit for aggressive material removal. Click the image to purchase 

Members have had great things to say about John Britt's new book, Mid-Range Glazes. Click the image to buy from Amazon.com

Purchase Glazes Cone 6 by Michael Bailey, The Potters Book of Glaze Recipes by Emmanuel Cooper, or Making Marks by Robin Hopper, all available at amazon.comMastering Cone 6 Glazes by John Hesselberth & Ron Roy is now out of print.

Harbor Freight is a great place to find unbeatable prices for better HVLP spray guns with stainless steel parts and serviceable economy models, as well as detail guns, all tested by our members for spraying glazes, as well as compressors to power the guns. As yet no one has tested and commented on the remarkably inexpensive air brushes at harbor freight.

The critter siphon gun is a spray alternative that is well liked by some of our members, and is available at amazon.

Amazon is also a competitive source for photo light tents for shooting professional quality pictures of your work. They also have the EZ Cube brand favored by several of our members. You might also want to purchase the book Photographing Arts, Crafts and Collectibles . . .

If you are up to creating videos of your work or techniques you might want to invest in a flip video camera

Following are a few scales useful for potters. Your final price could be less or more - things change.

American Weigh Black Blade Digital Scale, 1000g X 0.1g $11.08 

For the non-digitally inclined the old standard Ohaus Triple Pro Mechanical Triple Beam Balance, 2610g x 0.1g, with Tare $169.00

And finally a low cost clone of the OHaus. The Adam Equipment TBB2610T Triple Beam Mechanical Balance With Tare Beam $99.62

ebay is a great alternative for many tools and the equipment used in the ceramics studio - kilns, wheels, extruders, slab rollers are often listed there both new and used.

Tips for Members

If you just want to spout off, it is best accomplished as a blog posting. If you want to get more guidance and ideas from other members, ask a question as a new discussion topic. In the upper right corner of the lists for both types of posting, you will find an "+Add " button. Clicking it will open an editor where you create your posting. 4/16/2014

© 2019   Created by George Lewter.   Powered by

Badges  |  Report an Issue  |  Terms of Service