Yikes! My Slip Won't Dry

[Evezamora]

I just tried making paperclay slip from a recipe that I was given at a workshop.  The slip has turned out extremely runny and will not dry.

 

To a 50# bag of dry porcelain clay

 

Add to one qt of warm water • 7 grams Barium Carbonate • 13 grams soda ash

 

To a 5 gallon bucket add • 2 gallons of water

 

Add the barium carb mixture to the water and mix for 5 minutes, and while water is mixing:

 

get mixture ready • ¾-1 oz of sodium silicate • 1 oz Darvon • 2 oz of water

 

The paper pulp is made separately and added to the slip.  First, it wasn't clear that you don't add the pulp to the entire  5 gallons of slip, so I added it to 2 gallons.  

 

I tried dipping wire and after 30 minutes, it's still wet. I left both the slip and the paperclay slip uncovered overnight in hopes of evaporating water, but that hasn't helped.  I would really want to save this batch because I can't afford another 50# bag of porcelain.

 

 I wonder if there was too much deflocullent in the slip?  Can I save it by adding a flocullent like epsom salts?  Btw, are the epsom salts bought at a drugstore the same used in ceramics?

 

Aloha - Eve

[oldlady]

can you contact the person who gave the workshop and ask?  that is the source, maybe you just wrote down the wrong number somewhere.

 

 epsom salts is epsom salts whatever you use it for and wherever you get it.  mine came from the drugstore.

[cabako]

What kind of darvon? This is just a guess but maybe you added too much sodium silicate and darvon (higher concentration in 2 gallons compared to 5) and the mixture is more "oily" than wet, in which case it will never dry it will just be oily.  Darvon seems to be short or long chain polymers which might keep water in the wire droplets...

 

Another option is too much sodium silicate which is hygroscopic meaning it will pull moisture out of the air and stay wet. Or keep the water trapped inside.

 

I have never used paper slip, made slip or any of these items....Maybe add the water up to 5 gal final volume and see what happens.  

[Callie Beller Diesel]

Your mix sounds like it's gelled. What kind of porcelain did you use, and is there bentonite in it?

What is the reasoning behind deflocculating it at all? It doesn't sound like you're slip casting in plaster, where too much water is a detriment.

If you're just coating a thin wire or string I've not known deflocculating paper slip to be necessary.

[Evezamora]

I did contact the person who gave the recipe to me and she said that I should let the evaporate from the slip for the next batch.  I asked her about the deflocculating being a problem, but haven't received a response.

 

I did mix a small amount of epsom salts with water and added a few drops to a cup of the slip.  It made it slightly thicker, but didn't solve the drying issue. 

 

I used Darvon 7.  I have no idea why the recipe called for deflocculents.  I'm not doing slipcasting, just sculptural work.

 

I will have to check the type of porcelain when I get home.  I don't know if it contained bentonite.  What effect would that have on the slip?

 

I still have 3 gallons of slip without the paper added.  It has a definite sheen to it, both before and after it dries.  Not at all like the slip we used in the workshop. 

 

Is there anyway to reverse the deflocculation effect?

[Callie Beller Diesel]

Your clay supplier should be able to tell you if there's bentonite in the clay body. Some porcelains have it as a plasticizer, because many of the ingredients in porcelain make it short to throw with. Unfortunately, Bentonite+deflocculants=gelling. It could explain your drying issues. If you didn't know beforehand to specify to your supplier that you were deflocculating your slip, they may have sold you porcelain that had bentonite in it in error.

 

Deflocculating clay makes it more fluid with less water added. It's something you do for slip casting so you don't saturate your moulds too soon, or in some dipping slips so that the leather hard piece that is being dipped into slip doesn't absorb too much water and collapse. This is the first time I've ever heard of deflocculating paper clay slip. If you're dipping wire or string into your paper slip, I don't think deflocculating is necessary. The paper pulp should solve any shrinkage issues all by itself that would make the slip crack off under normal circumstances.

 

I don't know of a way to rescue this slip if it's gelled. That doesn't mean there isn't one, though. If someone who does more slip casting than I do wants to chime in, I'm curious too.

[neilestrick]

Your recipe is not too far off from recipes I've got for making casting slip. How watery is the slip? Once you've gone past the watery stage, the slip will thicken or gel. The only way to fix it is to add more dry material and water to dilute the deflocculant. Ideally, when making slip you add the sodium silicate and/or Darvan a little bit at a time, because each clay body will require different amounts to achieve the desired viscosity. If you just used all of the quantities in the recipe, you may have blown right past the desired state and into thickening/gel range.

[Evezamora]

Thanks everyone.

 

I used 50#s Laguna Toshi Porcelain Slip (no bentonite).  I added the clay and sod sil/darvon mix 1/3 at a time, paying no attention to how it was responding when I added the ingredients .  

 

I mixed it for over two hours. 

 

The word that comes to mind to describe the slip's current state is "silky."  It's the thickness of dish soap and super smooth.  It takes 1+ hours to dry on dipped wire.  The supplier told me I have too much water, but that doesn't explain the silkiness.  He recommended adding more dry clay.

[Magnolia Mud Research]

my recommendation for making paper clay is to visit

Vince Pitelka's Tennessee Technological University – Appalachian Center for Craft website.

 

go to:
https://sites.tntech.edu/wpitelka/

select SYLLABI AND HANDOUTS  from the index along the top banner on the website
https://sites.tntech.edu/wpitelka/handoutsinformation/

scroll about half way down to the Clays and Clay bodies section for the topic: Making Paper Clay

https://sites.tntech.edu/wpitelka/wp-content/uploads/sites/45/2016/03/Making-Paper-Clay.pdf

download the instructions for making paper clay. 

 

This works with all normal clay body recipes used for handbuilding and throwing.  Never heard of using paper clay for slip casting. 

 

I use vinegar instead of water to make the pulp and to dilute bagged clay to form slip because it keeps the clay from molding.  It does smell like vinegar.

 

LT

[neilestrick]

What are you using the slip for?

[Evezamora]

Paper pulp is added to the slip to make paper clay slip.  Used for sculptural work such as:

 

http://pyrogirlaspen.com/portfolio/paper-clay-recent/

 

It should be thin enough to dip, but thick enough that it can be spread on a plaster bat.

 

I found this John Britt video where he uses epsom salts to thicken deflocculated slip.  His preferred method is to just add more clay to the slip to get the right thickness, but not more water.

 

[neilestrick]

Are you dipping items into it, or casting it, or using it to join other pieces?

[Evezamora]

Dipping and sculptural.

[PeterH]

Has anybody any idea how fast slip applied to wire should dry, I don't

 

Usually slip applied to clay articles has some water absorbed by the slightyly dryer

clay, and is allowed to dry on the time-scale of the pot. While casting slip has most

of the water sucked out during the casting, and still takes many hours to dry.

 

In a not very successful search for slip drying on wire I came across this:

http://ceramicartsdaily.org/pottery-making-illustrated/article/additions-to-clay-bodies-metals/

The next stage is to coat the wire armature, either by brushing or pouring, with paperclay slip.

Each coat of slip is dried completely before the next layer is added, a process that can take

several days.