Getting a piece out of a mold.

[Min 3,110]

I'm posting this question from @Wolf, she is new to the forum and wasn't sure where to post.

Her question, taken from the Status Updates, is "How do you get a leather hard piece out of a mold? " 

[Rae Reich 477]

Yikes! It's probably gone past leather hard by now! If it doesn't drop out easily, there is a chance that there's problems with the mold design - this is assuming the mold is not a commercial one. Can the OP post a photo?

[Mark C. 4,573]

Make sure there are no undercuts in the mold-is it a homemade mold?and how many pieces?

[Rae Reich 477]

Undercut is when the lines of the piece curve inward in a way that prevents the piece from dropping out freely from the mold. Everywhere there is an undercut, there should be a division in the mold so that each piece can be removed without damaging the form. A commercial mold will have been designed to accommodate undercuts. Homemade molds can be learning experiences. 

[liambesaw 2,486]

Is it a plaster mold?  If so, the piece should separate itself when it's leather hard.  If it's some other material, probably not gonna end well.  I saw someone trying to use a silicone mold with disastrous results.  Silicone and plastic are good for concrete or plaster that self set, not as good for clay which requires drying.

[liambesaw 2,486]

Is it white?

[liambesaw 2,486]

So it's probably not a plaster mold

Edit: wolfs original reply to this was "no, it's not white". They edited to "what".  This edit is to clear any potential confusion.

Edited March 18, 2019 by liambesaw

[Rae Reich 477]

13 minutes ago, Wolf said:

I hope it’s not bone dry I haven’t seen it in 5 days

If your mold is white, it's probably made of plaster.

Clay poured into a small (under 12") plaster mold, and then poured out after a few or several minutes, will usually be dry enough to remove after a few hours. If you open it by removing the bands and separating the plaster parts, the piece should be dry enough to take out without distortion.  If you leave it in for a longer time, it will still probably come out fine  

When you poured liquid clay (slip) into the mold, did you let it set for a period of time and then empty out the extra slip? If not, you will have made a very solid piece instead of a thin-walled piece. 

If you just pressed a piece of clay into a one-piece mold, it can be removed as soon as the clay has firmed up enough to keep its shape. 

[Rae Reich 477]

Yay! When the clay dries completely in the mold, it will shrink (all clay does, from wet to dry) and can sometimes get hung up where it wouldn't if were only just dry enough to remove. If you do it again, open the mold sooner.  

[Rae Reich 477]

On 3/18/2019 at 12:31 PM, Wolf said:

It’s not dry yet but close. Plus the mold can’t be opened

 The shell that has formed by pouring casting slip into a plaster mold and then, after a short period of time, pouring out the excess slip, should not take more than a day to be firm enough to remove. Molds are usually opened as soon as the clay is firm. The piece then continues to dry in the open air. Leaving the form in the mold until dry, unless it is a very simple shape, is likely to cause problems with removal because the casting slip will have shrunk around curves. 

Removing the form sooner also lets the plaster mold dry sooner, making the next casting sooner.

Are you in a climate that is cold and humid? Drying times will often be longer than my generalized, 65-80 degrees F.

Are you casting a solid form, rather than a thin shell form?

[liambesaw 2,486]

Ah that's why!  It's an aluminum jello mold!  For ceramics plaster is much easier.

[Mark C. 4,573]

This looks like a slab piece pressed into a plastic or metal form-not a mold.Well maybe a jello mold?

The terms are a bit mixed up here.

[liambesaw 2,486]

To remove from that in the future you can wait til it stiffens a bit and flip it over and try to tap it out

[Mark C. 4,573]

Use some mold lube as well on form before putting the clay into the form

[Magnolia Mud Research 702]

I have learned (the hard way) to ALWAYS put two layers of thin paper between a metal or plastic mold for wet clay.  One layer is for sticking to the mold, the other is for sticking to the clay.  Also have an air passageway to the bottom of the mold to break the "vacuum" that can hold the nearly dry clay inside the mold.  

LT

[Rae Reich 477]

Jelly molds and bundt pans are designed to release their contents. Put a board over the opening, when the board and mold are turned over the contents should fall straight down and the mold can be lifted up, the piece will be on the board. As the others say, there are a few things you can do to make removal easier, next time. This time, let the clay keep getting drier and try the turned-over-to-a-board thing every day till it comes out. You might kind of smack the board down hard on your table to help jar the clay out, but don't try to pry it out.