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AndreaB

Glazing Bottoms

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Anything the glaze touches will fuse. If you are just worried about the glaze being close, you can put a broken shelf or other thing less precious that it -might- get stuck to.

Alumina can also be added to help prevent something from sticking. It will leave a white powdery surface. Kiln wash is made form alumina and kaolin for this reason.

 

And if you wait, I can show you what happens if you forget to clean the bottom of something entirely and put it on a shelf.... somehow I did this the other day.

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Do you have a foot on your pot?

What cone are you firing to?

If you have a foot and you know that your glaze does not run, it is possible to glaze the bottom of your pot but leave an unglazed foot ring.

No Foot, If you are low firing then you can place the pot on a spur, ie a 3 pronged thingie , can't remember the right word just now dang it,  which can be removed after firing . It leaves scars but are usually insignificant.

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In the UK we call the spurs stilts.

They work great on earthenware, and on stoneware so long as the pot doesn't imbed itself onto the stilt because you are firing too high and the clay softens, or the pot is very heavy.

What I do is not have a foot, then press the centre of the bottom in a bit when leather hard so it is curved in very slightly - this ensures that the pot sits still, and also if the stilt doesn't go out to the edge it means that any slight dimples in the glaze around the stilt points don't stick out enough to scratch the table top.

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Tim,

 

I call them "Stilts" as well.  That's what I have always heard them called here in the US as well.

 

I use them on my low fire work, when I glaze the bottoms.  Though, most of the time I just glaze inside the foot ring, and use an underglaze on the ring itself, if I want it to have color.

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I use stilts all the time, especially on spoonrests and mini dishes. I have also used them on plates. I use a Dremel to smooth out the little dimples left by the stilt so it's nice and smooth. This does leave a bit of a dull spot but haven't figured out how to get rid of that.

 

T

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In low fire ceramics you can glaze the bottom and use a ceramic 3 pronged stilt to hold your pot up off the shelve. These stilts come in two styles all ceramic with ceramic points or the other style is ceramic with metal points. Either way you bust the off and grind down the rough spot left behind.They work best in cone 06 work but can be used a bit higher. In high tempeture fires like cone 10 the pot will slump around them and they are not used.

What is your piece going to be fired to ?

A better way is to thrum a foot on the work and trim out the bottom leaving a foot for the piece to sit on and then you can glaze the inside bottom which is now up off the bottom of shelve and will not stick to the shelve.

I hope I made this all clear

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Thanks to you all for painting a clearer picture. I was a bit confused about using cookies for keeping the pot/bowl off the shelf.  Most of my stuff is trimmed with a foot ring.  I just don't like seeing the whole bottom of an item being a buff colour (I used high fire stoneware).

 

I was asking because I have a set of three leaf bowls and wanted to glaze the whole piece. As they are slabbed and already bisqued I can't put a foot ring on.  I also don't have any stoneware stilts.

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High fire stoneware is the firing temp.

 

You can glaze the inside of a foot ring. Personally I do not wax the ring, just wipe the glaze off with a sponge. If the foot has been compacted/wheel burnished while trimming it is very easy to remove the extra glaze. Then, as long as there is enough of a cut, the center spot can be glazed.

 

This works with bowls too.

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We still do not know what cone you are firing to?

Without stilts you cannot glaze the bottoms

So sorry Mark, I'm firing to cone 8, with a manual stop at 1260C.  I'm using proprietary glazes madr up by South African companies and all instructions are to fire to 1260. 

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Thanks for the cone as just saying high fire stoneware clay can still mean you are using high fire clay but firing it to lower temps . We have seen this many times over the years here of folks firing clay to much lower tens then it is intended for. I suggest not glazing where the contact areas are.

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Thanks Mark. I've not learned yet what difference a soak period makes.  I've a manual controller (me!) and have been ramping 150 deg per hour, leaving the last hour to switch off automatically. I've had good results so far and am curious to know what difference the soak will make..  

 

Using an electric kiln I know that I can't speed up the cooling time. But having said that, the manual controller usually starts a fire early afternoon and goes to bed when the last ramp is set, so I guess if I want to slow down the cooling I'll have to keep awake.

 

On the last point what results can I expect using slow cooling?

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When you soak a kiln the glazes mature and its also will raise the glass melts times meaning the cone will bend more as in a temp gain. Slow cooling also helps with certain glazes and is good on the equipment and furniture

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