slipcast Trouble pouring slip out of mold

[kath_of_khan]

Hello,

Apologies if this has been addressed before. I’m new to slipcasting. I recently bought a teardrop shaped Sundance Christmas ornament mold. I’m having trouble pouring the slip out of the mold. The opening is so small! I love the shape of the mold and really want to use it.
 

I’m hoping that there might be a trick to allowing the slip to flow freely out of the mold. More water to the slip? I’ve tried adding a little, but it seems to just stay in the mold. I’d love any help or insight. 
 

Thanks so much!

Kathryn 

[Jeff Longtin]

Good Morning Kath_of_Khan.

Welcome to the Forum.

Yes, adding more water, to the slip, is the solution. The slip may be too heavy in deflocculant but that can only be affected if you're mixing your own slip.

Another solution is to wet the mold before you pour. (The inside of the mold.) This will slow down the speed at which the slip sets. 

good luck

[kath_of_khan]

Thanks so much, Jeff! I'll try out both of these tips and report back! I’m using a cone 5 premade porcelain slip. 
 

I'm primarily a hand builder and wanted to try making my own molds. I thought starting out with premade molds would be a good way to try it out and see if I like the process. I have to say, I’ve learned a lot just using my little premade molds.

—Kath 

[Jeff Longtin]

fyi: a teardrop shape is probably one of the most difficult shapes to cast. You're not alone in having this problem.

Another suggestion: stick a small stick into the slip, every 5-10 minutes, and stir the slip around, gently. This way the slip will not set, entirely, and it should pour out more easily.

 

 

 

[Chilly]

Put a drinking straw into the opening as you pour the slip out. It prevents all the liquid trying to get out at once, and allows air in.

[kath_of_khan]

Thanks so much Chilly and Jeff! I’ll see if I can get a small straw into the pour hole—it’s so small!
 

But I’m really glad to know that it’s a difficult shape…power in numbers, right?

—Kath

[PeterH]

If the slip is pourable when you come to emptying the mould then an airlock is a possibility. As is narrowing of the opening if the walls are too thick.

However if the glaze is gelling it's a different problem -- think thixotropic house paint which sets on standing. 

The long-term answer is to adjust the slip until it doesn't gel during the time you are casting. Stirring the slip well just before casting (without introducing bubbles) can also give you a little extra time.  While Jeff's stirring approach can break the gel in the mould.

Long ago I was using a mould with a long thinnish  neck very next like this, and an unsatisfactory ready-mixed slip:

 Pushing the handle of an artists paintbrush down the centre of neck and pushing it up and down for a while (while avoiding the sides)  broke the gel in the neck for long enough for the mould to be emptied.

Edited December 1, 2023 by PeterH

[Jeff Longtin]

And lastly, an odd method that sometimes works...fill the mold up with slip...wait a few minutes...then empty the mold. Allow the slip to set up a little bit...then repeat.

(Essentially emptying the mold before the slip has a chance to gel.)

You can only do it a few times, and the casting will likely be thin, but it might allow you to cast the object and have a reasonable chance of it casting uniformly.

This only really works with porcelain. (Because it's a fairly dense clay.) It's quite something to cast an object that's eggshell thin and have it fire out.