firing a fitted lid

[chantalqtal]

hi

I´m making a porcelain container with a fitted lid (you can see cross section below) and intend to high fire (1255ºC) both parts together because of wharping. Any tips on how to prevent both parts from sticking together???

I´d really appreciate the help. Thanks 

[liambesaw]

You can use alumina wax, it's just wax resist with a little alumina hydrate mixed in.  

[Min]

Hi Chantal and welcome to the forum. Just to add a little to what Liam posted, 1-2 tsp of alumina hydrate to a cup of wax resist plus I would add some food colouring so this resist is a different colour than your regular resist. The alumina hydrate will want to settle out of the resist so stir it often while using. Also, when you use it be very careful not to get any of it on your glaze as it will fire to a very rough texture.

edit: with your gallery, if you make the inner part of the flange at a slight inward taper, not the right angle like in your image it makes the lid fit easier.

[Bill Kielb]

I would just mention that even with the alumina trick you likely will need to use whatever techniques you are familiar with to get these things apart. As long as the joint is not glazed then with some gentle persistence they should separate. The alumina will work it’s magic but it likely will not turn out to be “lift off magic”

microwave, gentle tapping ....... whatever you prefer.

[liambesaw]

5 minutes ago, Bill Kielb said:

 

microwave, gentle tapping ....... whatever you prefer.

Freezer, crowbar, hammer, wall 

[chantalqtal]

thanks - ill let you know how it works out. on Monday I´ll see bisque results. By the way- why mix alumina with wax and not just water or even leave it in powdered form???       ( I´m not glazing the outside, only the flat bottoms inside). have a nice day

[Dick White]

The wax will make the alumina powder stay on the surfaces you paint it on until you can put it in the kiln. Then the wax will burn up, but the alumina powder will still be there. With water or just the powder, it might fall off as there is nothing to make it stick.

[Bill Kielb]

Bisque to 04 won’t need Alumina. Alumina is not very soluble in water so getting it to stay where you put it is tough Powdered Alumina is very fine and will move around pretty freely and tends to get in any glazed areas, it does not melt below 3000 degrees. Let us know how it all works out and which you prefer after your glaze fire.

Personally I would explore the wax tip first

 

best of luck!

[oldlady]

a question about the design.   how wide is the final box?   there is no handle and i suspect you plan to make these stacking boxes.  there are no measurements showing so i hope you are considering the size of the hand that must span the entire top to lift the lid.

the design shows a very short lip on the bottom.  it will work better if tapered as Min suggests but i would make it just a little higher and provide a tiny bit of space between the pieces.  otherwise, it will be hard to use every time the lid is lifted and returned.

[chantalqtal]

thanks! I´m not commenting on the design yet - its  part of my final work for my degree -  ill surprise you with a photo - you'll need both hands to lift the lid and.....    

[Bill Kielb]

Your picture looks dimensioned as ........................... I better not say. Probably should remove the dimension line though

[chantalqtal]

haha - its not a state secret 

[andros]

Good morning

Let me please resume this discussion because I'm going just in these days to fire for the first time a fitted lid.

I've already read in the past about the use of wax resist with alumina for firing a fitted lids but, since I've never done it and I almost never used wax resist It's not still really clear how actually It should be done... that is: does the resist must be applied on the contact area before applying the glaze (in order to prevent the  glaze from going on that area) or does the wax resist could be applied on the contact area after the whole surface has been glazed (by immersion, for example) in order  to prevent the  glazed contact areas to stick together ?

[liambesaw]

Before it's glazed.  I usually fire lids on during bisque and firing them separated for glaze firings.  Much less headaches trying to get them apart.

[andros]

Thank you liambesaw !

[andros]

Sorry, just another thing... but, if wax resist is applied before glazing, why alumina is needed? Does is not enough a simple wax resist?

[neilestrick]

The alumina keeps the raw clay areas from fusing together, which they will do if you're firing the clay to full maturity. The wax allows you to apply the alumina, and works as a resist when glazing.

Always fire lids and their pots together so they don't warp.

[oldlady]

andros, i think English is not your first language and want to make sure you do not end up with a pot whose lid will not come off.  

plain wax is used to keep glaze off of an area that should not have glaze on it like the foot that will sit on the kiln shelf.    it is also used in decorating a piece so colors can be applied and separated or to use areas of fired clay without glaze as part of a decoration.

in addition, wax with alumina in it is used to keep the body of a pot and the lid of a pot separate so the lid can be removed when the pot is fired with the lid in place on the pot.     firing the two together insures that the lid and the body will fit together later.   the area of the pot and the area of the lid that will touch when put together should not be glazed.

[andros]

oldlady, you are right, English is not my first language. Anyway I think to have understood enugh since all your explaination are verly clear. The real obstacle to my understanding usually is not the language but my inexperience!

Really thank you!

[chantalqtal]

hi, I never thanked for the help received. the wax alumina resist works very well!