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Alumina And Wax

Got weird marks

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#1 Pugaboo

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Posted 25 July 2013 - 09:51 PM

You all might remember awhile back I asked about firing a lidded box. I asked about alumina and several people were very helpful in suggesting ways to fire the box with the lid on and not have it stick. Well I think I did something wrong...

I mixed 2 teaspoons of alumina with 4 oz of liquid ceramics wax. I then brushed this on the bottom edge of the lid and the top edge of the box including the flange. I let that dry then glazed the box with the lid on and fired it to ^6. Well on a happy note the lid did not stick at all! :) On a sad note in several spots it almost looks like the wax and alumina mix melted and ran down the side of the box leaving a permanent dull white dusty mark. :(

Boo hoo so what did I do wrong?
Did I use too much of it?
Should I only apply it to one edge not both?
Did I use the wrong kind of wax to mix with the alumina?

Can I use something like steel wool to sand as much of this mark off as possible them reglaze and refire it? I'm basically looking at it as a learning experience at this point so am willing to try some different things to see what happens. I have another lidded box that I am not going to glaze fire right away until I feel a bit more confident in its survival or at worst I'll fire the lid and the bottom separate and hope they still fit together afterwards.

So any suggestions anyone?

Terry
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#2 TJR

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Posted 25 July 2013 - 10:57 PM

Pugaboo;

I had a problem similar to this last year. I had porcelain trimmed feet sticking to the shelf. The term is called "plucking". I have a small dish of alumina hydrate and water. I mix this up so that it is in solution, then brush it on. While the piece is still centred, I brush the wax on over top of the alumina. You cannot drip any alumina on your glaze, as it is refractory, and will not melt.

TJR.



#3 Mark C.

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Posted 26 July 2013 - 12:14 AM

As noted alumina will not melt and needs to be handled properly. 

Over the years I stopped adding it to wax  ( as it settles out) instead I dip my cut sponge in wax and dip it into a small bowl of alumina powder.

You have to be careful it does not run down the pot. I usually only use alumina on 1/2 of the lidded form the top or bottom then just straight wax on the sponge on the other 1/2.This process is fast and precise . Let these two pieces dry before putting the lid on.Then after glazing I sponge the edge once more with a wet sponge to remove any glaze drops.

If the glaze gets any hydrate on it it will be rough and dry so you need to be carefull

 

Now as to your wax it burns off not runs off so thats not the issue. No matter what kind you use

I use mobil Ceramul A from Laguna-I think its sold in small amounts as I buy it in 5 gallons buckets-I use one up very 5 years or so.

As far as it running did that happen when you applied it? As thats the only time it can run down.

Mark


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#4 Marcia Selsor

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Posted 26 July 2013 - 06:56 AM

I have used alumina in wax on porcelain for many years and never saw anything like that. I usually just brush is one both sides and the bottom for porcelain.
I can only think that it may have dripped during application. Was your wax white?
For that process, I use the Aftosa wax.
I like it because it is bluish and can be seen. It can come off if you make a mistake and catch it immediately.
Marcia

#5 neilestrick

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Posted 26 July 2013 - 10:12 AM

I'm thinking maybe your wax was on way too thick if it ran. You only need one thin coat. Possibly too much alumina in the wax, too.


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#6 Marcia Selsor

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Posted 26 July 2013 - 10:19 AM

That's possible. I dilute the blue wax to get it to brush on easily.
Did you dilute your wax?

Marcia

#7 Mark C.

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Posted 26 July 2013 - 10:24 AM

I to add a bit of water to my wax to this it. You have to be more careful then as it runs even easier.

Mark


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#8 Chris Campbell

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Posted 26 July 2013 - 10:33 AM

Isn't 2 teaspoons of alumina to 4 oz of wax a lot? I use less and am wondering if this proportion is right?

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#9 Marcia Selsor

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Posted 26 July 2013 - 10:57 AM

I use less too. But I add it to diluted wax. Probably about 2 tsp to 8 oz.
Marcia

#10 neilestrick

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Posted 26 July 2013 - 02:48 PM

If I read the pst right, the alumina/wax ran in the kiln, not during application. Otherwise it would not be on top of the glaze, it would leave an unglazed bald spot. Only really thick wax could run like that as it melts.


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#11 clay lover

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Posted 26 July 2013 - 03:11 PM

I am confused on this topic. why are folks using alumina? if the 2 edges that come together are not glazed, what is the reason to use alumina? Is using alumina over the glazed surfaces keeping them from fusing together? Please help me get better infirmed. I just wax the touching edges and glaze, put the lid on and fire. What am I missing?

#12 OffCenter

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Posted 26 July 2013 - 03:25 PM

I am confused on this topic. why are folks using alumina? if the 2 edges that come together are not glazed, what is the reason to use alumina? Is using alumina over the glazed surfaces keeping them from fusing together? Please help me get better infirmed. I just wax the touching edges and glaze, put the lid on and fire. What am I missing?

 

In atmospheric firings it prevents the salt, wood ash, etc from forming a glaze there. In other firings, like cone 6 electric, some clays, especially porcelains, fuse together if there's not a thin layer of refractory material there. She could have used wadding on her boxes but alumnia is usually handy and easy.

 

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#13 Marcia Selsor

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Posted 26 July 2013 - 03:26 PM

Porcelain tends to fuse to itself during the glaze firing. Sometimes the feet also fuse to the kiln shelf. So using Alumina prevents both of these things from happening.

Marcia

#14 clay lover

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Posted 26 July 2013 - 03:41 PM

Thanks for the clarification. If kiln wash is used on the shelves, does that take care of the fusing, or is the alumina also needed on the feet ?

That might explain why every once in a while my 'not really porcelain' ^6 porcelain has minor breakage on a foot ring. One will and the one next to it won't.

#15 neilestrick

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Posted 26 July 2013 - 03:45 PM

If your kiln wash is relatively fresh, it should do the job just fine.

 

Putting alumina in the wax is not a mistake, by the way. I've been doing it that way for years with no problem. Wax and alumina in one step, quick and easy.


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#16 Pugaboo

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Posted 26 July 2013 - 05:18 PM

Thanks everyone for your input. I think from what I have been reading that I simply put it on too thick. I over compensated by putting too much on the 2 lips trying to prevent the lid from sticking.

What I have done so far is used my Dremel tool to smooth out the boiled looking spots until they are smooth and level with the glaze around them. They were raised and sort of looked like they sitting on top of the glaze to start with. Doing this of course left some dull areas. I finished by scrubbing the whole thing really well and it is now drying.

I would like to try and reglaze it just to see what happens, how do I do this? I think to get the new layer of glaze to stick to the old I need to heat the box up and then quickly apply the new layer of glaze; am I right? Since the clay is fully vitrified can I refire the box and lid separately this time around? Do I need to refire both the top and the bottom or just the bottom? Also do I need to reglaze the entire box or just put glaze on the dulls spots?

Thanks for your help... I stumped my teacher as well... Oh well if I gotta screw up at least I can do it creatively.

Terry
The world is but a canvas to the imagination - Henry David Thoreau

#17 Min

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Posted 27 July 2013 - 11:08 AM

It’s easier to reglaze a piece with glaze that has some of the water evaporated off so the glaze is thicker, or scrape some of the glaze off the side of the bucket if you have some thick glaze stuck there. Heat the pot up, 200F or thereabouts. Brush the glaze on, let dry and repeat. Also, there is a product called Apt II that works really well to thicken up glaze and also helps the glaze adhere to the pot, you just add a few drops to 1/4cup or so of glaze.

 

I would fire with the lid on, 2 reasons why; firstly when you refire any glaze other than clear the glaze can look different from just one firing, more fluid, thinner etc. Secondly, the box could shrink or move a bit in the 2nd fire and the lid will no longer fit. You might get bloats from doing a 2nd fire, but you have nothing to loose in trying. If possible put pieces that are getting a 2nd fire to top temp in a cool part of the kiln.

 

I would use alumina as others have suggested for this firing. It might be an idea to see if you really do need alumina between lid/gallery in the future. You could try a mock up lid, just a scrap 1” or so  base with a snug lid, unless you are using a porcelain or porcelain like clay you might not need to. The clay I use does usually result in the lids sticking when fired but a light tap with rubber mallet around the pot loosens it up with no plucking.

 

Min



#18 Pugaboo

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Posted 07 August 2013 - 05:15 PM

Wanted to give an update on this question. I used a Drexel to grind off the rough marks where it looks like something ran down the side of the box. I took these spots down to the same level as the glossy glaze since they were raised. I then applied new glaze to these areas. I used the alumina and wax again on the lid and rim but this time I applied a very light coat and even used a paper towel to wipe any off that had not dried by the time I was finished applying it to the edge.

I refired it successfully! The glaze blended in beautifully and no runs! You can't actually tell I had to grind off some and reglaze it. The top didn't stick either GRIN. I fired the other lidded box for the first time as well and doing the alumina and wax like I did worked perfect on it too, no runs, marks or stuck lid!

So I think my original problem was just too much wax so that it ran as it heated up and the alumina stuck to the glaze and was fired right into the top layer of it. Thank you everyone for your help.

Terry
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#19 oldlady

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Posted 07 August 2013 - 05:26 PM

glad to see you back here.  was beginning to worry.


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