Keba Hitzeman on sun 22 aug 10
A friend of mine just moved to Colorado, I inherited her 5 never-opened
bottles of Amaco 15-S casting slip and don't know where to begin using this
stuff. I am familiar with slip-casting, but have never done it - I've bee=
n
doing a lot of googling to find information on mold-making and what to add
to it for color.
What has worked well for anyone in the Pub who is "slip experienced"? Any
"oh my gosh, I wish I had known..." pearls of wisdom for me?
Thanks,
Keba
(one week before school starts and clay is relegated to evenings and
weekends...sigh.)
--
**********************************************
Keba Hitzeman
Pleasant Hill OH
www.yellowroomarts.com
Dannon Rhudy on sun 22 aug 10
You can use this slip just as slip, and
you need not cast it if you don't want to.
It lasts a long time if sealed, and I've
noted that slips made for casting are amenable
for use on a number of different clays. You
could be set for life - depending on the size
of the bottles, of course.
If you do want to make a mold(s) for casting
purposes, there's a lot of folks on the list
who slip cast. They'll no doubt send help.
regards
Dannon Rhudy
John Rodgers on sun 22 aug 10
Keba,
The slip - after some adjustments - can be cast directly into molds to
create forms. It can also be diluted somewhat and used for decorative
effect by application with an airbrush. It can also be used for surface
decoration with ordinary decorative brushes. Stains can be added to it
for colors. Also, you can acquire a polymer compound from Coloriffic
Porcelain (http://www.colorificporcelain.com/) - find it at the end of
their list of porcelains - called GOOP that when added to the slip per
the instructions, makes an extraordinary clay body that can be rolled
out into very thin sheets which can then be made into very thin,
flexible flower petals, leaves, and a whole variety of things that
require immense flexibility without tearing - something that ordinary
pottery throwing clay cannot do without great difficulty in handling.
I mentioned adjusting the slip.
1) For casting purposes - porcelain slip works best if the density is
adjusted to be between 1.70 and 1.80. I personally prefer 1.75. If I
have a lot of work, then I will start with 1.70 and as I recycle the
clay I allow the density to rise to 1.80, but if the slip density is
above 1.75 when I start, I will first adjust it downward towards 1.70.
If it is 1.75 at the beginning, for a few pieces I will go ahead and
cast with that. The density is adjusted by the balance of water vs clay
present. It is expressed as simply the ratio of the weight of a given
volume of water to the same volume of slip. Weigh a pint of water,
then weigh a pint of slip. Next, divide the weight of the slip by the
weight of the water. The slip with it's heavy components (clay) will
weigh more than the water, so when the numbers are divided, the results
will be 1.x with the "X" being the fraction thereof. You are looking to
get 1.75 ideally. If the number is to large - ie, greater than 1.75 -
you need to add with just a bit of water.If to small, then add a bit
more slip back to the mix. Ideally, for the purposes of adjusting the
slip, you need to pour out some slip on a plaster slab and let it dry
out completely, then store it for the purposes of adjusting the slip. It
is much easier to adjust the slip with dry clay than trying to add wet
slip during the adjustment. Dried porcelain slip re-integrates easily
into the slip mix when stirred vigorously with a jiffy mixer.
2) Viscosity - you need to adjust the viscosity of the slip as well. It
may well be OK right out of the container - but then again - maybe not.
Leave nothing to chance here. The viscosity of the slip is nothing more
than the flow rate of the slip. You need a viscosity cup and they come
in different forms. The simplest, easiest to use, and least expensive
one I have found for purchase was from New Mexico Clay.
http://www.nmclay.com/Amazing/searchresult.asp The part is called a
TL497 Viscosity Cup. Slip viscosity is adjusted by adding a deflocculant
like Darvan or Sodium Silicate diluted to 50/50 with water. I much
prefer the latter myself. To learn about this, visit the Laguna Clay
website at this link.
http://www.lagunaclay.com/support/art-of-slipmaking.php
Ignore the part of the Laguna instructions when they talk of the 500 ml
flask and all that - the weighing of the slip as I described above will
get it done cheaply and effectively. The same is true with checking the
viscosity. The simple viscosity cup works just fine. But do get an
understanding of the rest of the document. It's important.
BTW - since you are not mixing slip from dry mix, but simply adjusting
slip already made - don't worry about soda ash and the like. But you do
need to know about the sodium silicate.
I hope this helps answer your questions.
Good luck in your endeavors.
Regards,
John Rodgers
Chelsea, AL
www.Moldhaus.com
On 8/22/2010 8:43 AM, Keba Hitzeman wrote:
> A friend of mine just moved to Colorado, I inherited her 5 never-opened
> bottles of Amaco 15-S casting slip and don't know where to begin using th=
is
> stuff. I am familiar with slip-casting, but have never done it - I've b=
een
> doing a lot of googling to find information on mold-making and what to ad=
d
> to it for color.
>
> What has worked well for anyone in the Pub who is "slip experienced"? An=
y
> "oh my gosh, I wish I had known..." pearls of wisdom for me?
>
> Thanks,
>
> Keba
> (one week before school starts and clay is relegated to evenings and
> weekends...sigh.)
>
> --
> **********************************************
> Keba Hitzeman
> Pleasant Hill OH
>
> www.yellowroomarts.com
>
Snail Scott on sun 22 aug 10
On Aug 22, 2010, at 8:43 AM, Keba Hitzeman wrote:
> A friend of mine just moved to Colorado, I inherited her 5 never-
> opened
> bottles of Amaco 15-S casting slip and don't know where to begin
> using this
> stuff. I am familiar with slip-casting, but have never done it...
Number one in importance, I think, is
mold design. 'Draft' is the term for how
far a vertical surface has to be from
true vertical to be able to pull the mold
off readily. ('Vertical' in this case means
parallel to the direction you are trying to
pull the mold section!) I use an upside-
down fast-food paper cup as a model for
student reference: it's pretty close to the
right slope. Learn to find the right location
for parting lines by keeping draft in mind,
and that's 80% of what's needed for
good mold-making.
Next in importance, I think, is thickness.
Make it too thin and it's crazy-fragile;
too thick and it doesn't set properly in a
reasonable time frame. Since thickness
is created by the amount of time the slip
stays in the mold, timing is critical. The
longer a mold is in active use, the more
moisture it soaks up from the slip, so the
longer each casting will take to set to the
same stage, but you will get a feel for it.
To check thickness, use a toothpick or
something similar to judge the thickness
at the opening of the mold - it will be
pretty similar throughout.
Have fun, and good luck!
-Snail
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