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Store Bought Clay Slip Is Way Too Thick...

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I've been slipcasting for ages now and always just purchased clay slip in the USA. It always arrived in the right consistency in a box and never had a problem. I'm now in the UK and purchased some slip and instead of being chocolate syrup consistency, it's thick like a very thick milkshake and in plastic jugs (not full). Obviously this won't work for slipcasting. I emailed the warehouse but no reply and I'm unable to call out at the moment. What am I missing? Am I supposed to water this down? Did I order the wrong product? Any ideas?

 

It's a clay stoneware slip from Scarva.

 

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I am not a slipcaster, but I have purchased slip in the US that was as you describe.  My experience is it may be thixotropic and will thin out with agitation, or it may need sodium silicate to deflocculate it some and thin it out without water addition.  Since there is headroom in the container, it may be that UK ships it so it may be adjusted on site.  With no experience with the Brit way, if it doesn't thin our with agitation, I would wait for experienced help.  Hopefully the warehouse will respond.

 

You might also try Scarva for technical information at:

 

http://www.scarva.com/Information.aspx?TranslationLargeID=02

 

John

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^this.  being commercially made, the water content is likely where it needs to be, and the slip needs to be adjusted (with a deflocculant).  sodium silicate or darvan would be a good place to start.  perhaps decant some of the slip into another container and add a drop or two of darvan to see if it helps and go from there.

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Wait for advice from Scarva.  My friend buys buckets of slip from local supplier, but the are from potclays.  Earthenware, but she uses them "straight from the bucket", so I don't think there is a USA way and a UK way, maybe just a Scarva way.  It would make sense to ship slip minus half it's weight of water, but then I would expect there to be "instructions" for use.

 

Good Luck, welcome to the UK and please tell us more about yourself.

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Grrr... thanks for the advice and info. I'm rather grumbly about this as the whole reason I buy it ready made is to not have to deal with deflocculating or any other nonsense. I'm also irked at the non-reply to my email as their website seems to indicate that email is the quickest way to get a reply and it's been four days. Headed over to a friends to use her landline and hopefully get an answer to this. Grumble grumble grumble... 

 

About me? Well I jumped straight into slip casting to make tiki mugs for a friend and then got tricked into making poltergeist clown doll replicas from the movie Poltergeist... which is what I'm trying to make right now. I've made about 12 of them in the past. I'd love to do teapots though. As soon as I get a place with space and some free time (ha!) I'm totally going to make some quirky teapots.

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I have been using ready made slip for the same reason. I keep some deflocculant on the shelf because the ready made stuff sometimes needs tweaked. My goal is to gradually use some of my clay reclaim for slip and get on to mixing my own slip as soon as possible.

 

Sounds cool Love to see some pictures. I have a complicated tiki mug that I will be molding today... Just hope it comes out well.

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This is the reply I got... 

 

If you shake the slip as best you can and add to a bucket and then stir you will find it
should be more fluid.
If still too thick add a small quantity of water 250-500mls of water.

 

Hmmm... will give it a go, but it's REALLY thick so I find it suspect. It's too thick to even pour out of the jug!

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If you stir ithe slip hard and for some time (e.g. with a paint mixer) does thin down. If so it

sounds like the problem might be excessive thixotropy.

 

If it remains thick ... duh! Perhaps start by measuring its density.

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You need to measure the specific gravity. Even if it was commercially made slip you need to be able to check to see of it was made right. Sometimes mistakes are made and checking things like SG can save you from using faulty materials and wasting a whole production cycle. The material supplier can readily replace faulty materials but may be less likely to compensate you for lost time and firing costs.

 

If the SG is correct and it is too thick then as mentioned it is either thixotropic and needs a good stir or it is under deflocculated (in which case the supplier messed up)

 

Check the SG.

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Well, as it's too thick to pour out of the container I swiveled the handle of a wooden spoon (as the spout is too narrow for the spoon part) in it for ages and ages... still too thick to pour out, so I added water in stages (a little bit more than 500ml total) and I still think it's too thick, but I've mixed and mixed and mixed and poured in. 

I must say... slipcasting something this big in a carpeted third floor flat is not ideal. I miss my heated garage with workbench!

 

Will look into the technical stuff for future. I must say I'm a bit lazy about doing all that work as it's not interesting to me and I guess I'd been lucky with great suppliers in the past.

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Might be an idea to ask Scarva what the specific gravity should be. If you have scales it will take about 5 minutes to figure out if you needed to add water or a defloc or both to the slip.

 

It's really not very technical, a quick way to measure s.g. is to just weigh out 100 grams of water in a clear plastic cup, or better yet a narrow test tube, then mark where the water comes to with a sharpie on the outside of the cup. Dump out the water, dry the cup and pour slip into the cup up to the line.

 

Weigh the slip and move the decimal point over 2 numbers. So, if the slip weighs 180 the specific gravity would be 1.8  If the s.g. that Scarva gives you is less then add water until your test amount is the same as the s.g. from Scarva. If the slip is too thick to pour after you have corrected the s.g. then add some deflocculant until it is the consistency you want to pour it at.

 

There is a good article on defloccing slipcasting slip here: http://digitalfire.com/4sight/education/understanding_the_deflocculation_process_in_slip_casting_213.html

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