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Lorraine76

Slip Casting Big Vases. Is It Possible?

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Hello Everyone.

 

One of our client asked us to make 15-20-25 liter holy water reservoir.   The size of the 20 liter reservoir would be about : height 42 cm. The 25 liter a bit bigger. The form should be rotund/tubby.

 

We usually make our products with hand building and slipcasting. But we have never tried to make such "big vases".

 

My question would be if it would be possible to slipcast such sizes? Has anyone tried to slipcast these kind of reservoirs? These are mounted with taps at the bottom.

 

The size of the 20 liter reservoir would be about : height 42 cm. The 25 liter a bit bigger. The form should be rotund/tubby.

               

 

thanks for your advice in advance!

 

Nandor

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I have seen large slipcasting molds like this, but remember that much plaster is HEAVY... There's usually rigs for holding / pouring out slip, large catch buckets, etc. It's definitely a process.

 

I've also seen people do large pieces like this with slipcast sections. Split the vases into two halves and join them (slip & score), blend the line, and you won't be able to tell much of a difference.

 

Either way, it's a good bit of work. But definitely do-able.

Lorraine76 likes this

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Toilets are made by slipcasting, so why not big vases? Seems to me that the main considerations would be available work space, storage space, and figuring out the mechanics of pouring the excess slip out of the huge and heavy mold once it reached thickness. You'd probably have to construct it so it could be mounted on a pivot with a lever for dumping. Seems excessive for a one-off job.

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I had a book from the library, (cant find the details) but it showed how to put a bung in the bottom of the mould so it could be drained. Think it was a Lark Ceramics, but not the Clay Lovers Guide.......

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I just made a few plaster molds

Unless your committed to making more of these I'd. Just build it and not cast it. Like me gecko says. It's will be a huge mold taking up storage space. You would have to sculpt / make master, Any way.

I'm not saying can't be done,

Look at all the cheap foreign made large vases. Yes slip molded.

 

Plus I think liturgical wares should be hand made, they, excuse the pun are more soulful.

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Made a series of Greek urn vases for while, one 28cm tall x 22cm diameter the other 38cm tall x 32cm diameter, not as big as what you are proposing but...man...the work involved in making them was astounding....making pots to begin, then making the molds, then the slipcasting, then firing even glaze....etc

 

The actual slipcasting needed 2 people each time to empty the HEAVY molds and twice the straps holding the molds gave out leaving the floor awash with slip that took weeks to clean well....

 

Agree with others....unless this is a repeating well paid job, or you can reuse the mold for other jobs, or this is a real labour of love....then for a one off item handbuild it by coiling, or around a safe burnable former......otherwise save yourself some of the drama and look for a commercially made mold (eBay, Craigslist or new if need be), it will be expensive upfront but save you hours of labour in the long run.

 

My 5cents..

Irene

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Hi All!

 

Thanks for the useful advice! So it seems that it is possible to do this. Of course it would be more pieces, hopefully..., because of 1-1 reservoire would think of this method. So one important aspect is the weight and the pouring out, because it is really a lot of slip in it....

 

My other issue is what kind of slip to use, because i am not sure that the one we use for small pieces would be suitable for this because of the size....wont it collapse? or does it only depend on the thickness of its wall?

 

thanks

 

Nandor

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My other issue is what kind of slip to use, because i am not sure that the one we use for small pieces would be suitable for this because of the size....wont it collapse? or does it only depend on the thickness of its wall?

 

thanks

 

Nandor

 

What cone are you firing to?

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At low fire temps you won't have any issues with the clay slumping since it's not going to vitrify. I think you should be able to get away with using the same slip. Maybe make the piece a little thicker so its easier to handle when it comes out of the mold.

 

Since you're going to be putting a tap at the bottom, would it be possible to use the opening for the tap as a drain hole for the mold? Just put a cork in it during the casting process, then pull the cork and let it drain out from there. It would prevent you from having to pick up and turn the mold while full. There might be a little bit of slip left in the bottom, but once you had most of the slip out it would be much easier to turn it over to finish the draining.

 

The other option if it's too heavy to lift and turn, is to build hooks into your mold so that it can be hooked up to an overhead hoist.

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How would you get a vessel that would hold water if you put a drain tap in the bottom of the mold, since the liquid slip in need of draining would be separated from the tap by the layer of slip solidifying into the vase?

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I'm assuming from the original description that there will be a tap added on the side of the jug, near the bottom. A hole could be left there in the mold for the slip to drain out. If the hole plugs up during the casting process, just poke a hole in it to let the slip out.  The hole can then be cleaned up when it comes out of the mold.

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There might be a little bit of slip left in the bottom, but once you had most of the slip out it would be much easier to turn it over to finish the draining.

 

You can use a turkey baster to slurp up any left-over slip.

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Hello Everyone!
 
It's been almost a year since i asked you about slipcasting big items/vases. We have done it in the meantime. 15-20 L. water fonts with tap at the bottom.
I try to attach some photos of the mold.
Well it wasnt easy. Casting is also tiring from buckets, but it was the first such bigger size we tried.

At the bottom of the mold we attached a copper tube and through that the slip can be drained. From the bottom, the leftover can be taken out with a bigger sponge.

The biggest issue was the weight of the mold! Was really heavy......

 

Thanks for all your support and ideas!

 

Hope this can help someone in the future and if anyone has any questions regarding this topic maybe i can help too.....:)

 

Nandor

 

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Rather fond of the "torch" trick myself. When I do press molds pf sushi, bowls. etc: they get flamed to set them up. Nothing like the smell of steaming clay to motivate you to make another piece. Okay, so I use it to hasten production... it works.

Nerd

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