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Member Since 04 Oct 2011
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#96339 Centering Tools

Posted by neilestrick on Yesterday, 10:05 AM

Centering is not just a position on the wheel. It is a state of being. All these tools do is get the clay into the middle of the wheel, which leaves you with a mass of clay that is not smooth, consistent and homogenous. You must cone the clay at least a couple of times (3 is the magic number) to get it mixed and evened out before worrying about whether or not it's spinning perfectly in the middle of the wheel. If you 'center' the clay with this tool, it will go out of center at you open the clay, because the clay was not coned and mixed. The only time I would recommend using a tool like this is if you have strength or movement limitations.

#96173 Shipping Lidded Vessels

Posted by neilestrick on 22 November 2015 - 11:47 AM

Pots break during shipping when they can clang together, so everything in the box has to be either separated by cardboard, or taped together so they can't move. I often put lids on the pots, inverted, with a couple layers of foam padding in between. Then I cover the entire piece with foam or bubble wrap or paper, just to keep the tape from sticking to the pot, and use packing tape to secure the lid and pot. Wrap it all the way around several times in every direction so the lid can't move. I also use this method for other pots, separating the with 2 layers of foam sheets and taping them up. Sets of cereal bowls, small cups, pots nested inside other pots, etc. As long as they are bound tight and can't clank together, they survive.


Then, when you pack the pot in the box, use pieces of scrap cardboard around the pot, essentially creating a smaller box inside the shipping box. There should be at least 2 inches of peanuts between the inner and outer box, all around and top and bottom. The flat sides of the inner 'box' will keep the pot from migrating through the peanuts, and also add an extra layer of protection.


I never use bubble wrap, unless I happen to have some from a shipment I received, and even then I only use it for tape protection. Bubble wrap does a really poor job of protecting rims and edges unless you wrap many layers, which gets pretty pricey, and it adds too much thickness for taping things together. Foam sheets provide good cushioning without adding a lot of thickness, and protect rims very well. In general, though, if you do a good job with peanuts and boxes, you don't need any foam or bubble wrap unless you're taping pieces together.

#96171 How Do I Stop Water Leaking Out From The Space Between Ceramic Kitchen Top An...

Posted by neilestrick on 22 November 2015 - 10:58 AM

Yep, caulk is your friend.

#96138 Glaze Cracking And Dropping Off Pot Before Firing.

Posted by neilestrick on 21 November 2015 - 11:36 AM

It's a lot of magnesium indeed. It's way above limits, as is the boron. The alumina and silica are at the very bottom of limits. 10% tin and 2% cobalt are also a bit excessive. This is not a good glaze for functional work. It's not forming good glass.

#95435 Making Sodium Silicate.

Posted by neilestrick on 07 November 2015 - 10:54 AM

neil, where do you shop?


I just did a quick search and found it at Axner for $2.50/pint.

#95422 Making Sodium Silicate.

Posted by neilestrick on 07 November 2015 - 09:24 AM

It's cheap. Just buy a pint. I don't know what it costs in England, but here you can get a pint for $2.25.

#95318 Kiln Not Reaching Temperature

Posted by neilestrick on 05 November 2015 - 10:03 AM

The exit flue is in the top center? How big is the exit flue?


I'd say the burner is definitely too close to the port. With the kiln being that close to the wall, you're going to calcine the cement wall and weaken it.


Using that type of controller on a gas kiln is far from ideal. Gas kilns require constant pressure inside the kiln in order to maintain evenness, and the damper must be adjusted accordingly as the temperature increases. Cycling the gas on and off like and electric kiln just doesn't work very well at all.


Can you override the controller and fire manually?

#95317 Interesting Dervelopment In Glass.........

Posted by neilestrick on 05 November 2015 - 10:00 AM

Very interesting! That's going to be some expensive glass, though. Not a simple process, and Tantalum is quite rare, one-fifteenth as common as gold.

#95201 Oxblood Glaze, How To Have A Green Where The Glazed Is Not Reduced

Posted by neilestrick on 03 November 2015 - 11:56 AM

A celadon base will get you a get start to a copper red, but reds generally need a little more melt than celadons. It's a fine line between runny enough and burning out the copper. You'll often find that copper reds have very low clay content in the recipe, which make suspension and application trickier. Copper reds also need something to be the nucleus for the copper crystal, which is why they use tin oxide. Historically iron was used, but it tends to darken or muddy the glaze more than tin. Most copper reds that I have seen actually use very small amounts of copper, as low as 0.25%, but generally not more than 1.5%.

#95138 Oxblood Glaze, How To Have A Green Where The Glazed Is Not Reduced

Posted by neilestrick on 02 November 2015 - 02:12 PM

That is not an area of oxidation. The area where it is not red has most likely had the copper burned out by contact with the flame in the kiln. It is going green because of the iron in the stoneware clay. Technically, the glaze there is clear, not green. Put your pots near the edge of the shelf where they are likely to contact the flame and you'll be able to get this effect.

#94705 Underfiring..?

Posted by neilestrick on 24 October 2015 - 10:34 AM

How long is the distance from your kiln to the electric circuit?  In an earlier post, you mentioned using a heavy duty extension cord.  You lose power the longer the distance it has to travel from the circuit box to the kiln.  My guess is you are not getting full power due to distance. 


The power situation could prevent the kiln from reaching temperature, but if the cone is bending and the sitter is shutting it off, then the power is not an issue.

#94563 What A Crack! ( In Pottery )

Posted by neilestrick on 20 October 2015 - 08:28 PM

I would never make a lid for an existing pot, because as you're finding out, it's not worth the hassle. You've already had 2 failures, which means at best your profit will be 1/3 of what you quoted the customer. In the end you could end up basically doing it for free. I would also never make a lid for a pot that I didn't make in the first place. You have to decide whether you want your customers to by YOUR pots, or if you're just there to make what they demand. Would you ask Warhol to replace your damaged Picasso?


As for why the lid cracked, big wide lids like that love to crack. You're probably right that it wasn't able to shrink the way it wanted to, or it heated unevenly. 3/8" is a little thick IMO, so that may have contributed as well. Try putting some silica sand on the shelf next time. It acts like little ball bearings and allows the piece to move.

#94260 Orton Cones

Posted by neilestrick on 15 October 2015 - 04:07 PM

It's hard to tell from the photo, but the angle of your cones seems like it's off. From the photo it looks like the cone is set into the pack with it angled toward the end of the pack, which would mean it will try to bend along the spine rather than the flat edge, which is what it looks like it's trying to do, which would explain the odd bend.

#94183 Qotw: Right Or Wrong? Japanese Worldly Wisdom....

Posted by neilestrick on 13 October 2015 - 08:56 PM

I think this can be interpreted in several ways. If I understand this as it was meant by the Japanese, then perfection comes from the absence of ego, that there is perfection in selfless action. But when I first read it I thought it simply sounded like a slacker's mantra- why bother trying at all. As I thought about it more, I came to the conclusion that perfection becomes more difficult to achieve because we are pushing the limits of our abilities, but it doesn't mean we shouldn't still strive for perfection. It's not a reason to give up. Why not try to be the very best you can be? And it doesn't mean that less-than-perfect results aren't acceptable. Every attempt is a necessary part of the education needed to achieve perfection.

#94145 How Much Clay Per Inch?

Posted by neilestrick on 13 October 2015 - 10:28 AM

It's not a constant amount, because as pots get bigger they also get thicker, and the proportion of clay in the bottom vs. walls also changes. It also depends on how wide the piece is. I can make a 4 pound pot that's 14 inches tall or 6 inches tall.