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jrgpots

Member Since 15 Mar 2013
Offline Last Active Oct 01 2016 09:38 PM
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#112298 Very Cool Ulexite Oil Spot Glaze, Cone 6

Posted by jrgpots on 30 August 2016 - 11:27 PM

I found a very nice oil spot glaze posted on Facebook by Clara Giorello.   She took a cone 10 oilspot glaze, "Daly's oilspot" and changed it to a cone 6 glaze by adding Ulexite.   I had not even heard of Ulexite before, so a google search taught me that Ulexite is a sodium borate mineral.  It is also known as Sodium Calcium pentaborate octahydrate.  It sounds like very cool stuff.  It forms complex crystals that refract the light.  It is known as "TV Stone."   It is similar to Colmenite without the Silica and alumina.  Gersley borate has a small amount of it.  Clara Giorello ground the mineral herself.

 

Her recipe is: cone 6

 

K feldspar           40

quartz                 30

Talc                     10

Kaolin                 10

Ca Carb              10

 

 

add:   RIO           10

          Ulexite       10.

 

 

I tried to find a supplier for Ulexite.  I found an import company that was willing to sell me a metric ton of the stuff.  Has anyone ever used this and by chance found a distributor?

 

Jed

Attached Files




#111391 Coma Clay

Posted by jrgpots on 14 August 2016 - 09:21 PM

 

 

Marcia: I gave it the name "coma", because the clay has no memory. 0.18% MGO, 0.31 FE.. ultra white at bisque/maturity.

 

:)

 

Nerd

 

 

Coma clay...........If  you fired it beyond the point of vitrification ,, you call it "Coma-toast".    .......just a thought. :D

 

All kidding aside, it looks great.




#110741 My Kiln Build

Posted by jrgpots on 29 July 2016 - 08:47 PM

I am finally getting around to build my kiln.  It will be about 16 cu ft in capacity.   the outer measurements are 43' x 43."

Here are the first pics from the project.   More will follow.

 

Jed

Attached Files




#110306 Your Refractory Is Toast

Posted by jrgpots on 19 July 2016 - 11:45 AM

If you soaked the loaf of bread in Sodium silicate and compressed the loaf with a 10- 20 ton press prior to placing it in the chamber, then fired it in an Argon environment, you would have silicon carbide.....a kiln shelf.

 

There is a great article Feb 2005 Science daily about making petrified wood using similar technique.   They placed wood in acid to breakdown the cellulose a bit, then soaked it in hot sodium silicate.  It went into an Argon oven and came out petrified.    So you could make a kiln out of wood if you wanted to..

 

 

Jed

 

http://www..sciencedaily.com/releases/2005/02/050210005224.htm




#110230 How Much Granular Manganese Dioxide?

Posted by jrgpots on 17 July 2016 - 08:03 PM

I have used basalt granules instead of manganese to speckle my white clay body. i have used 20-40 mesh grains in a concentration between 2 - 4 %. It is not toxic and gives a nice cookie and cream appearance.... just a thought.  It also doesn't play too badly with any glazing.




#109604 Birdhouse In Chinese Red

Posted by jrgpots on 29 June 2016 - 10:06 AM

wrens like to fill up any cavities that might entice other birds to move in too close to the wrens.  and their babies return to the house for some time after they begin to fly.  yesterday, the mother scolded my dog for walking into her yard.  

 

 

Years ago we had a pair of wrens claim our enclosed atrium.  We left a small upper window open.  The window had no screen.  So once the nest was made, we did not close the window until all the wrens left the nest an didn't return at night... The music was great. They sang as we ate breakfast.  Watering the atrium plants was not so easy.

 

  The nest was in an old discarded pot.

 

 

Jed

 

 

 




#107946 Mixing Clay Bodies To Get Desired % Shrinkage

Posted by jrgpots on 01 June 2016 - 07:10 PM

As Min mentioned, both clay bodies are cone 5, so it will not be as bad as mixing earthenware and stoneware.  it will be more like adjusting shrinkage by adding grog.  The changes in shrinkage comes from the added grog content.  I hope.

 

Yes, I use a shrinkage ruler.  I  measure the % shrinkage from wet (fresh out of the extruder) to bisqued as well as from bisqued to  vitrified. Knowing the amount shrinkage at each step makes it easier to predict hole placement.

 

I want to clay with a little tooth in it for strength, but more importantly I want to get as close to 10% shrinkage as possible.  I make Native American flutes.  The diameter and length determine the fundamental pitch, key and hole placement. Just a mm difference can drastically alter the sound.  I  tune the flutes after the bisque firing and tune then flat by  the amount shrinkage will occur in the final firing. Tuning at this point is much harder

 

My issue is that since I just got a new extruder, I need to make new tube dies.  My old dies don't work in the new extruder.  So, since I have to make new dies, why not try to simplify my calculations. I want the final tube diameters to be 1" and 3/4" after firing. Everything would be easier. For example, if the shrinkage were 10%, the linear length would be .90 of original and the area would be .81 smaller (almost 0.8).  I can calculate these in my head. It makes it much easy for hole placement and tuning.  But first, I have to make new tube dies.  Is everything as clear as mud?

 

I have about 100 lbs to play with  so the "test, test, test"-ing will start tomorrow. 

 

Jed




#107877 Community Challenge #6

Posted by jrgpots on 01 June 2016 - 12:53 AM

Has anyone thought about a more abstract self portrait?

 

Jed




#106339 Metal And Arcing In An Electric Kiln

Posted by jrgpots on 05 May 2016 - 02:15 PM

If the nails were galvanized, the galvanized material will "burn off." It kind of looks like sparking.

 

Jed 




#105351 Attempt At The Vintage Look

Posted by jrgpots on 17 April 2016 - 10:04 PM

I just finished this plate.  I wanted an old or vintage look as if it were from the turn of the century.  The clay is a buff colored and reclaimed, cone 5 reduction.  Barnard's slip was applied to the greenware with a mild sgraffito patterned. Licorice black was applied in the crevices then and a local clay glaze was applied to the piece. 

 

Does it look vintage to you?

Is it successful?

 

Jed

Attached Files




#104643 Planning For Shrinkage

Posted by jrgpots on 03 April 2016 - 03:53 PM

So find the diameter of you measuring tsp (assuming a sphere shape spoon) and divide by 0.6815. This will give you the diameter of you greenware spoon.


You mean volume, not diameter, right?
The volume of a sphere is 4/3 x pi x r3. So you can devide the volume by 0.6815...True.

And, since the volume of a sphere equation has only 1 measurement of distance, the radius, you can divide the radius by 0.6815 and get to the same place. The radius may be hard to measure, so measure the diameter instead. It is easier.

So the Answer to your question is: you can get the right adjustment by dividing the volume or the diameter. It will end up the same. This is unique to the sphere.

If you are making a cylinder, divide the volume by 0.8615.
OR
You could divide the height by 0.88 and the diameter by
0.7744, which is 0.88 x 0.88. This is because volume of a cylinder is..... pi x r squared x height.

As a side note, this is why mugs proportions look different after firing. The fired height will be 0.88 of its prevoius height while the diameter will be 0.7744 of its diameter.

Jed


#104608 Planning For Shrinkage

Posted by jrgpots on 02 April 2016 - 10:57 AM

It would be really hard to work with clay on the moon  since it would loose all of its water content even before the first firing. :P   But what a great question...I understand that the ryolithe on the moon is very abrasive.  I would hate to throw with that type of clay too.   Some of you guys who like to "throw dry" might even struggle.  I wonder if you had a pressure controlled environment with O2 on the moon, would it be easier to pull a cylinder in the decreased gravity?  would the clay tend to fly off the wheel more?..... Babs, you started a whole new set of questions someone could ponder over for years... B) .

 

 

Jed




#104594 Planning For Shrinkage

Posted by jrgpots on 02 April 2016 - 12:28 AM

Just for fun, I calculated the needed volumes (in mls) of greenware mug sizes to make 8, 12, and 16 oz fired mugs. Mind you, I calculate these based on my math and have limited experience on the wheel.

8 oz fired cup.... 12% shrinkage.....347.18 ml greenware.
15% shrinkage.....385.28 ml greenware.

12 oz fired mug.... 12% shrinkage ....520.75 ml greenware.
15% shrinkage.....577.90 ml greenware.

16 oz fired mug.... 12% shrinkage.....694.35 ml greenware.
15% shrinkage.....770.56 ml greenware.


Mark, Marcia, John, Neil, and others with the experience do these values sound right?


#104593 Planning For Shrinkage

Posted by jrgpots on 01 April 2016 - 11:26 PM

Let me throw a wrench in the calculations.
1. As mentioned the length will shrink by .88.
2. But, the area will shrink 0.88 x 0.88 or 0.7744.
3. A Volume will shrink 0.88 x 0.88 x 0.88 or 0.6815.

What does this mean?
1. It means that the volume of 1 tsp will shrink to 0.6815 of its volume after firing.
2. If you want to make a tsp volume after firing, you will need devide your prefired volume by 0.6815.

Now let's assume you want to make measuring spoons in a half a sphere shape. This means the diameter of the greenware spoon needs to be 1.136 larger.

So find the diameter of you measuring tsp (assuming a sphere shape spoon) and devide by 0.6815. This will give you the diameter of you greenware spoon.

This is assuming an average shrinkage of 12%.
If you clay shrinks 13% then you would need to devide by 0.87 x 0.87 x 0.87 or 0.6585.
If you clay shrinks 15%, then you would devide by 0.85 x 0.85 x 0.85 or 0.6141.

This is because the volume reflects the cubed value of the shrinkage .....(4/3 pi r cubed).

Everyone got it?

Jed


#104543 Community Challenge #5

Posted by jrgpots on 31 March 2016 - 10:47 PM

Attached File  ceda rbreaks-2.jpg   165.58KB   0 downloads

 

This is my final entry.  Unfortunately it cracked to pieces... :huh: Next time I need to compress the tiles more.   The good news is that all of the glazes I made by hand.  The green matte did not show as many streak marks in testing as on the tiles.  But, I really like the texture of the tree... :)

 

Jed