Alumina And Wax

[Magnolia Mud Research]

The wax is just an adhesive to hold the alumina in place.  The wax burns away. 

LT

[Rae Reich]

On 3/16/2019 at 8:54 PM, Magnolia Mud Research said:

The wax is just an adhesive to hold the alumina in place.  The wax burns away. 

LT

...leaving a fine coating of alumina, which can be brushed or washed off after firing. A sufficient coating of alumina is what prevents sticking.

[allenc27]

Thank you guys so much, that's a lots of info. I will try the tap method and get some alumina hydrate for future teapot.

[Ceramicheights]

Hi all, this thread has saved my sanity and I have been using alumina hydrate for a while now. I don't normally wax my pots, so I just paint it on, mixed with water.  Sometimes it can be difficult to totally remove the alumina after firing. I'm wondering if anyone has experienced this issue and has any suggestions. Thanks! Amanda

[Min]

Hi Amanda and welcome to the forum 

Alumina hydrate is not known for being difficult to remove, it just dusts right off. I'm wondering if you're getting a bit of glaze on it, where are you using it, on lid galleries or ? Also, you're 100% sure it's alumina hydrate and not something else?

[liambesaw]

7 minutes ago, Min said:

Hi Amanda and welcome to the forum 

Alumina hydrate is not known for being difficult to remove, it just dusts right off. I'm wondering if you're getting a bit of glaze on it, where are you using it, on lid galleries or ? Also, you're 100% sure it's alumina hydrate and not something else?

Eh it seems to stain my red clay with a dusty white that doesn't come off, I have to use sandpaper.

[oldlady]

the wax is used to separate areas of glaze.  if you do  use wax plus alumina to separate the pieces the alumina should just become dust once the wax burns off.

[Ceramicheights]

Hi Min, and thanks! Long time reader, first time poster. There is a 100% chance that something has contaminated my jar. I'll mix some pure tonight. (There are lots of plates to fire.)

I use it for the bottoms of bmix and porcelain pots to prevent plucking. 

5 hours ago, liambesaw said:

Eh it seems to stain my red clay with a dusty white that doesn't come off, I have to use sandpaper.

I used just lightest dusting this time. I sanded the bottom of my plate and still had to wash it off. I swear there are still faint brush marks on the porcelain.

It's not residual glaze, but I had wondered if that was the problem.

[Min]

10 hours ago, Ceramicheights said:

I use it for the bottoms of bmix and porcelain pots to prevent plucking. 

Might want to think about your kiln wash too. If Bmix is plucking I'm thinking your kiln wash might need a re-coat. Do you make your own kiln wash (which recipe?) or use commercial stuff? 

[douglas]

On 3/2/2020 at 7:21 PM, liambesaw said:

Eh it seems to stain my red clay with a dusty white that doesn't come off, I have to use sandpaper.

I use a cone six red clay and it comes right off. However when I use it in cone 10 that sometimes happens. I think your clay may be over firing if the alumina gets embedded in the clay. I still use it in cone 10 but I know I will have more clean up and finishing later when I do. 

[liambesaw]

3 minutes ago, douglas said:

I use a cone six red clay and it comes right off. However when I use it in cone 10 that sometimes happens. I think your clay may be over firing if the alumina gets embedded in the clay. I still use it in cone 10 but I know I will have more clean up and finishing later when I do. 

My red body is very fluxy, it plucks on the shelves too

[Ceramicheights]

On 3/3/2020 at 8:52 AM, Min said:

Might want to think about your kiln wash too. If Bmix is plucking I'm thinking your kiln wash might need a re-coat. Do you make your own kiln wash (which recipe?) or use commercial stuff? 

Hi Min, I stopped using kiln wash a while back. It seemed to only be good the first couple of firings and then would start flaking off.  It was a kiln wash mix from my clay supplier.  It seems easier to grind the shelves than to repaint the kiln wash, and now I can flip the shelves and I've been doing it for a number of years. I do think that when the shelves get nasty, they reek havok on all my pots, not just bmix and porcelain.

[Min]

7 hours ago, Ceramicheights said:

Hi Min, I stopped using kiln wash a while back. It seemed to only be good the first couple of firings and then would start flaking off.  It was a kiln wash mix from my clay supplier.  It seems easier to grind the shelves than to repaint the kiln wash, and now I can flip the shelves and I've been doing it for a number of years. I do think that when the shelves get nasty, they reek havok on all my pots, not just bmix and porcelain.

Much of the commercial kiln wash is made up of what is cheapest, ie silica and kaolin and little of what makes a good kiln wash expensive which would be the alumina hydrate. If you do decide to start using kiln wash then try making your own wash. 50% alumina hydrate, 25% calcined kaolin and 25% kaolin. 

[MC Steve]

On 7/26/2013 at 1:14 AM, Mark C. said:

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

I was excited to see your advice since I have been having this very problem with my clay lidded jars.   I would like to try Alumina however an online search reveals all sorts of varieties:

Research Grade a Alumina Powder 10-15nm, Research Grade a-Alumina Oxide Nanopowders 150-500 Nano, Alumina 30c (Health and Beauty) 

Can you advise which type I should get?

[oldlady]

hello and welcome to the forums.   where are you looking?  the pottery supply companies have all kinds of pottery related chemicals.  try Clayworks in alexandria, baltimore and richmond.  or one of the big ones online.

Edited December 8, 2023 by oldlady
correct supply co name

[Mark C.]

Alumina Hydrate from any ceramic distributor is what to use-not something off the net for beauty products

Its a costly material these days but worth it-I buy it in 50# bags but its sold by the #

[klaklay]

Wondering if anyone has suggestions on how to remove all the alumina from the foot once its been fired ? It leaves a white dusty stain that I can't seem to get rid of ...

I mix a small, small amount of alumina into my wax and will often use black mason stained clay. The alumina dust just looks awful afterwards, but least my foot is not chipped

 

[Mark C.]

alumina brushes right off unless its got a fuzed binder mixed in. I dip my was spone in alumina in a bowl and way my galleries where lids meet the pot-wax burns of at cone 10 and alumina is back to a dust powder form and comes righ off. Does the mason stain fuze to clay and trap the alumina as its not melted at all????

[rox54]

I've noticed that the key, to whether the alumina is difficult to remove, is not using too much, regardless of the clay. I only fire to cone 6 (using pyrometric cones) and havd had it happen, so I am now more careful as to how much I apply. I apply it with water, not wax. Good luck!

[Callie Beller Diesel]

If you run a bit of 220 grit wet/dry carbide sandpaper (I get mine at Canadian Tire), it should take off stubborn alumina remnants. If you feel fancy, you can tack some to a bat and make a quick and dirty polishing wheel. 

[rox54]

I had some alumina fall inside a teapot. Does anyone know if that is food safe? The interior is white, but you can see it even after it was fired. Would the lemon test be indicative?

[Callie Beller Diesel]

A lemon test won’t rule anything in as safe, but it will rule out things that are susceptible to acid. That said, alumina isn’t a super volatile material in ceramics, and generally* adds to the durability of a glaze. It’s pretty refractory. That said, if it’s a dry, powdery lump of kiln wash sticking out of the glaze, that’s not good for craftsmanship or aesthetic concerns. You could try glazing over it and re-firing. 

Even if the alumina was not bonded and someone ate out of this piece, you also have to consider whether there’s enough material there to do damage to anyone. I’m not saying you should leave kiln wash bits embedded in your piece. I say that only to contextualize potential risks.

*assuming the rest of your materials are also within reasonable parameters, and the glaze isn’t already an alumina matte, which would be a logical assumption in a liner glaze.