May Luk on mon 30 jul 07
Hello all;
I am adding slipcasting into my workflow because I am trying to skip reclaiming. I make slurry from leftover clay, then I add soda ash and liquid glass to the slip. I pour and log my time and the thickness of my finished ware. This is what I think I can do to create my own recipe. I am still experimenting. I am dismay to find that I have to sieve the slip before I pour. This is messier than reclaim!! I don't recall doing that when I used to make slip for slipcasting working in a pottery.
My questions are:
1-Can I reclaim the wasted greenware from the mould? I was taught not to, but I would like to get a second opinion.
2-If #1 is yes, do I have to 'defloc' again? As the clay was not in suspension, but the sodium is still in there somewhere.
3-This question is to do with vocabulary. Is slip also called clay slop? Is the word 'slop' pertains to glaze only?
Thanks in advance
May
Kings County, US
John Rodgers on tue 31 jul 07
May,
I work with slip casting a great deal. I will try and answer your questions.
1) Wasted greenware from the mold can be reclaimed. I do it all the
time. Each time you cast, the trimmings and any crashed pieces can be
thrown back into the reclaim bucket and mixed back in with your slip.
Everytime you do this however, the density of the slip and it's
viscosity changes. Most slips work best at a density of 1.75 to 1.85.
Weight equal volumes of water and slip, and then divide the weight of
the water into the weight of the slip and you have the density of the
slip as compared to the water. Over time you will need to adjust the
slip density by adding water, since the slip casting removes water from
the clay, you will need to add some back into the mix.
2) De-flocculation - always adjust your slip density BEFORE you attempt
to defloc the slip. Otherwise you will create all kinds of problems. To
determine whther your slip even needs de-flocculation, after the slip is
adjusted for density, the first step is to do a viscosity test to
determine flow rate. With my test equipment, flow should be 23 seconds.
If my flow is slower - ie, takes longer, then I add sodium silicate (cut
50/50 with water) a bit at a time until the flow rate is at 23 seconds.
Then the slip is ready to cast.
If you add too much, the slip will begin to thicken. In which case you
must add more raw clay and some water and basically start your
calculations again.
3) Vocabulary - I clay slip clay slop? No, not really. clay slip has
very specific chemical makeup, physical properties, and handles
diferently from clay slop. It has a definte purpose and was designed
that way. Clay slop is not that way. It's very hap-hazard. in it's makeup
Regards,
John Rodgers
Chelsea, AL, USA
May Luk wrote:
> Hello all;
>
> I am adding slipcasting into my workflow because I am trying to skip reclaiming. I make slurry from leftover clay, then I add soda ash and liquid glass to the slip. I pour and log my time and the thickness of my finished ware. This is what I think I can do to create my own recipe. I am still experimenting. I am dismay to find that I have to sieve the slip before I pour. This is messier than reclaim!! I don't recall doing that when I used to make slip for slipcasting working in a pottery.
>
> My questions are:
> 1-Can I reclaim the wasted greenware from the mould? I was taught not to, but I would like to get a second opinion.
> 2-If #1 is yes, do I have to 'defloc' again? As the clay was not in suspension, but the sodium is still in there somewhere.
> 3-This question is to do with vocabulary. Is slip also called clay slop? Is the word 'slop' pertains to glaze only?
>
> Thanks in advance
> May
> Kings County, US
>
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