Richard C. Aerni on mon 25 mar 96
Hello everyone,
Thanks to one and all who have sent me suggestions for solving the thick
slip problem. There are a number of things I have in mind to try. I've got
about 30 lbs. of kaolin calcining in the kiln right now (many of your pots
in there too, Tom and Debra), and once that comes out, will get to mixing,
deflocculating, blunging, and testing. As soon as there are any significant
results, I'll post and let folks know.
Thanks again,
Richard
2975 County Road 40
Bloomfield, NY 14469
Phone (716) 657-6045
Fax (716) 657-6023 call before faxing
email rcaerni@cyber1.servtech.com
"...if it don't kill me, I'll be a better man for it..."
Henry Pope on tue 26 mar 96
At 10:17 PM 3/25/96 EST, you wrote:
>----------------------------Original message----------------------------
>Hello everyone,
>
>Thanks to one and all who have sent me suggestions for solving the thick
>slip problem. There are a number of things I have in mind to try. I've got
>about 30 lbs. of kaolin calcining in the kiln right now (many of your pots
>in there too, Tom and Debra), and once that comes out, will get to mixing,
>deflocculating, blunging, and testing. As soon as there are any significant
>results, I'll post and let folks know.
>
>Thanks again,
>
>Richard
>
>2975 County Road 40
>Bloomfield, NY 14469
>Phone (716) 657-6045
>Fax (716) 657-6023 call before faxing
>email rcaerni@cyber1.servtech.com
>
>"...if it don't kill me, I'll be a better man for it..."
Hello Richard - I pass along to you the slip that has enhanced another
potter's ash-glazed pots:
The g-string slap-on slick thick slip:
Neph sy 20
Spar 20
Silica 20
Ball 40
Simple. It works. Can't be too thick. I've used OM-4, but would try Sagger
xx, as the current notion seems to be that it has fewer problems. This slip
will work on bisque, though needs to be thinner. The originator, Rob
Forbes, applied the stuff with a three inch paint brush in thick swabs. He
fired to cone 5. It is currently being used at cone 10. Enjoy - HP
Hluch - Kevin A. on tue 26 mar 96
Clayartistes,
This reminds me...I recall seeing some quite nice pots of Rob Forbes but
have not seen much of his work lately...Does anyong know what's become of
him and if they have an address to add to my address list?
TIA
Kevin
> will work on bisque, though needs to be thinner. The originator, Rob
> Forbes, applied the stuff with a three inch paint brush in thick swabs. He
>
SLPBM@cc.usu.edu on wed 27 mar 96
Richard,
here's an odd idea but may work. If you know the shrinkage of your clay,
say 15%, you could calibrate your slip for the same by doing wet tests
on a slab and measuring that too. Might work.Also might want to try the
shrinkage idea on glass to reduce friction to see if shrinkage is radically
greater there than with the tooth of clay grabbing the slip as it shrinks.
Let me know how you solve the problem.
Alex Solla
Levine Meg Jessica on sat 6 apr 96
I did a lot of experimenting with thick slips last year.
My favorite: Forbes White Slip + 30 % Grog
Ball Clay (OM4) 50
Talc 20
Neph Sy 20
Flint 10
50 mesh grog 30
for a whiter white add 10% zircopax
dark green (color will run with a clear overglaze) 6% copper
Note- if the slip dries too quickly or is applied over long stretches of
a rounded surface, it may crack a little. Glaze will usually fill in the
cracks.
I use this slip for decorating with a pastry bag. It is fun to make as it
whips up ( when mixing with a hand-held mixer) and starts to form peaks like
meringue.
Levine Meg Jessica on sun 7 apr 96
Here is a repost of the thick slip recipe as I realized I forgot to include
the the cone it fires to. I have fired it cones 06-03 in oxidation.
Meg
I did a lot of experimenting with thick slips last year.
My favorite: Forbes White Slip + 30 % Grog
(for greenware)
Ball Clay (OM4) 50
Talc 20
Neph Sy 20
Flint 10
50 mesh grog 30
for a whiter white add 10% zircopax
dark green (color will run with a clear overglaze) 6% copper
Note- if the slip dries too quickly or is applied over long stretches of
a rounded surface, it may crack a little. Glaze will usually fill in the
cracks.
I use this slip for decorating with a pastry bag. It is fun to make as it
whips up ( when mixing with a hand-held mixer) and starts to form peaks like
meringue.
Gordon Ward on wed 28 sep 05
It seems that Darvan 7 exaggerates this phenomenon.
Gordon
On Sep 27, 2005, at 4:25 PM, mel jacobson wrote:
> and of course several of them just melted into a
> pile on the table. thick slip on damp greenware is tricky.
> it is imperative that the walls of the pot be consistent in thickness.
> a thin spot will suck up water in a heart beat. splat.
> it was funny however to walk into the studio the next morning and
> see about every 5th one...melted into a small pile on the table.
Linda Mccaleb on sat 19 sep 09
=3DA0 I bought some slip from a supplier in buckets. The buckets were not a=
ir=3D
tight. So the slip got really thick and we added water, we have added a lo=
=3D
t of water and are worried that there is too much.=3D0A=3DA0=3DA0We are usi=
ng a h=3D
ydrometer.=3D0A=3DA0=3DA0Should we use a deflocculant? If so, how do we kno=
w how =3D
much to use?=3DA0 =3D0A=3DA0 They are in air tight buckets now.=3D0A=3DA0 T=
hank you,,=3D
=3D0A=3DA0 Looking foreword to your reply, please help,=3D0A=3DA0 Linda=3D0=
A=3D0A=3D0A =3D
Snail Scott on sun 20 sep 09
On Sep 19, 2009, at 6:08 PM, Linda Mccaleb wrote:
> =3DA0 I bought some slip from a supplier in buckets. The buckets were =3D
not=3D20
> air tight. So the slip got really thick and we added water, we have=3D20
> added a lot of water and are worried that there is too much.
> =3DA0=3DA0We are using a hydrometer.
> =3DA0=3DA0Should we use a deflocculant?
If the only problem was evaporation of water,
than adding more should cure the problem.
The original deflocculant is still in there.
Add small amounts of water at a time, since
the purpose of deflocculant is to allow small
amounts of water to have a huge liquifying
effect. It shouldn't take much.
If too much water is added, let the slip sit
around uncovered to re-evaporate the excess.
Also note that some slips are more thixotropic
than others, and will seem very thick until
stirred.
-Snail
John Rodgers on mon 21 sep 09
Linda Mccaleb wrote:
> I bought some slip from a supplier in buckets. The buckets were not air=
tight. So the slip got really thick and we added water, we have added a lo=
t of water and are worried that there is too much.
> We are using a hydrometer.
> Should we use a deflocculant? If so, how do we know how much to use?
> They are in air tight buckets now.
> Thank you,,
> Looking foreword to your reply, please help,
> Linda
>
>
>
>
Linda,
Whilest a lot of folk use hydrometers - I don't. I much prefer using a
scale. I feel it's more accurate.
It sounds as if you may have added too much water, so before going
further, you really need to determine the density of the slip.
Do this by weighing equal volumes of slip and water. Say a pint of slip
and a pint of water. Put your container on the scale - zero the scale -
then fill your container with slip or water. This way you weigh only the
slip and water - and not the container too. Once you have got your
weights - divide the weight of the slip by the weight of the water. The
number you derive is the relative density of the slip as compare to the
density of the water. The number you derive should be between 1.75 and
1.85. If you number (density) is less than 1.75, then you have added to
much water, and will need to let some of the water evaporate until you
can get that 1.75-1.8 range. If the number(density) is greater than the
1.85 - then you need to add just a bit of water. But do so very
carefully so you do not thin the slip too much. Add a little water,
thoroughly mix, then weigh again. Takes a little time, but very accurate.
Once you have the density correct, you need to test the viscosity or the
flow rate of the slip. Tod do this you need a viscosimeter of some sort.
Now there are all sorts of expensive devices out there - and one clay
supply company sells as their standard equipment a 500 ml Erlenmyer
Flask with a two hole stopper and some tubing for $25-$30 but it is both
a waste of money and royal PITA to work with. Best to use the KISS
principle here. All you need is a container of some sort with a 1/8 inch
hole in the bottom. There are ready made devices like this available
from paint stores that sell house paint so you can thin your paint
properly. Works perfect for testing slip - and only costs about 5 bucks.
Here is link to a clay company that sells these and it's where I get mine.
TL497 Viscosity Cup - cost $5.75
http://www.nmclay.com/Amazing/itemdesc.asp?ic=3DTL497&eq=3Dsliptl497&Tp=3D
To use this cup, just dip into the slip and fill the cup. The slip will
drain from the hole in the bottom. The time should be 23-25 seconds.
No muss, no fuss, no corks, and tubes to wash between tests, not flasks
to wash between tests. Just dip and let drain, then rinse,. Very simple.
At this point - if your density is correct - 1.75 to 1.85 - and the flow
rate takes longer than 30 seconds - you need to add some silicate or
darvan. NEVER add straight silicate or darvan. Always mix the silicate
or darvan with water in a ratio of 50/50 before adding to the slip,
otherwise you will create an monster in the bucket!!! Add just a few
drops at a time and mix well in between times. Then test the viscosity.
Repeat until you have the slip flow rate inside of the 30 second mark.
You can try and get it down to 25 or even 23 second, but variations in
the clay may make it difficult to get it dead on. 25 seconds will work
just fine. If the slip seems to begin to thicken again, they you have
added to much silicate or darvan and you will need to add more clay and
start the process over.
Like I said, I much prefer the use of the gram scale because of the
accuracy.
Good luck.
John Rodgers
Chelsea, AL
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