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Working with Porcelain Clay

Marlyn's head

Marlyn’s head

I bought a bag of porcelain clay from Dick Blick. The white stoneware I’ve been using is just too rough for my tiny work. They say porcelain is very hard to work with, but I love a challenge!

First a little research:

Tips: from Gwendolyn Yoppolo

  • Adding softer clay onto a form that is too dry results in cracking.
  • Altering and/or bending a form that’s too dry or leather hard causes warpage and cracking.
  • In general, join only pieces of similar dryness and reinforce all joints with extra clay and compress them together with a rib.
  • Slow and even drying is critical.
  • Periods of rest, where the pieces are wrapped in an airtight chamber to slow drying and redistribute moisture, do help. The clay has a chance to get used to its new form at each phase, without having one part dry too quickly for the rest of the piece.
  • Another valuable technique is to restrict movement of the piece during the drying phase.
Here is a loose guideline and timeline for when to do what while working with porcelain. The phases are not distinct, but are separated out from the continuum of the entire process for the purposes of discussion. In fact, they blend together in many ways, especially the “cheese” sections. Because porcelain is thixotropic, it has a nice way of resoftening once it has reached the hard cheese stage, so you can actually go back and perform some soft cheese processes. Porcelain also rehydrates locally to some extent, so you can go back in a concentrated area. These guidelines are designed as a starting point for you to figure out your own way to achieve success.

Phase: wet clay -forming (additive)
Processes Supported:

  • throwing on the wheel
  • hand building
  • molding elements

Things to Remember:

  • pay attention to the space inside of your vessel  –  you are shaping this receptive space first, and will make the walls around it match
    ____________________________________________________________________________________________________________
    Phase: soft cheese        altering and building (additive)

Processes Supported:

  • changing the form’s shape
  • adding onto the form
  • other additions (handles, knobs)
  • texturing surface

Things to Remember:

  • slip and score all joinings
  • compress joints with a metal rib or wooden tool
  • perform any bending of the walls or altering of curves
    _____________________________________________________________________________________________________________________________

Phase: hard cheese               trimming and refining (subtractive)

Processes Supported:

  • trimming
  • rasping away areas of form
  • cutting away clay
  • carving patterns

Things to Remember:

  • basic form should not be altered
  • perform subtractive processes to lighten form or add aesthetic elements
    ___________________________________________________________________________________________________________________________

Phase: hard cheese         trimming and refining (subtractive)

Processes Supported:

  • trimming
  • rasping away areas of form
  • cutting away clay
  • carving patterns

Things to Remember:

  • basic form should not be altered
  • perform subtractive processes to lighten form or add aesthetic elements
    ____________________________________________________________________________________________________________________________

Phase: stale cheese            dry shaping (subtractive)

Processes Supported:

  • clean surface up
  • lighten form further
  • soften edges
  • trimming or scraping with rib
Things to Remember:
  • just before the piece is bone dry, it responds very well to having its surface scraped or trimmed
  • if the work has become bone dry, you can sponge it down to do some of these processes
    ___________________________________________________________________________________________________________________________

Phase: bone dry           erosive action (subtractive)

Processes Supported:

  • sponging
  • some light carving

Things to Remember:

  • sponging the form down reduces sanding, erases unwanted marks, and softens edges
  • don’t add too much water!
    ___________________________________________________________________________________________________________________________
Artists who sculpt in Porcelain:
Fawn Zeller, Marlaine Verhelst, Susan Scogin, 
and Loretta Norcross typically choose 
to sculpt original works in raw porcelain clay 
without the use of molds.
Others such as Jill Nemirow-Nelson may prefer to 
start sculpting from simple castings
 - simple hollow skeletons they can then manipulate.
For the resultant work to be called "original", 
these castings must be made from molds 
drawn from this same artist’s original sculpt!

Molds
If molds are used at all, these castings typically 
have minimal detail so most of the 
sculpting is done via direct clay manipulation.
The cast clay is promptly removed from the mold 
before it is even leather-hard. In 
this very wet and extremely fragile state,
they start to sculpt with complete sculpting 
freedom yet do not have to worry about 
hollowing out later!
If Fawn worked from molds at all in creating 
any of her original sculpts,
she would remove the clay almost before the greenware stage 
so she could immediately start 
re-shaping them.
Many times, Fawn simply started by picking off clay 
from a blob of thickened slip and 
shaped it into her basic forms.
She always tried to hollow her sculpts before firing.

Make it hallow
Most clay must be hollow before it is fired 
so that all the clay is a consistent 
thickness in hopes that it will all vitrify at the
same rate without any distortion. Fawn Zeller hollowed 
her pieces in the traditional 
manner by cutting them in half,
removed the excess clay in the center, 
then carefully rejoined the backs to the fronts.
Marlaine Verhelst starts her sculpts by laying 
her clay down over a Styrofoam form which 
when removed leaves a hollow consistently
thick sculpt ready to fire. As noted above, 
others start off with a set of simple hollow 
castings.
But Susan Scogin works so small (at 1:12 scale) 
that she claims she often doesn't need to 
hollow her work at all before firing!

Venting
All hollow items must be vented so all air can escape 
or the porcelain might explode in 
the kiln as any trapped air violently escapes!

Keep it Moist!
Early NIADA artist, Fawn Zeller, started sculpting 
in the customary manner by manipulating 
porcelain clay in a moist, leather hard stage
- always keeping it moist throughout the sculpting process. 
While working in this traditional manner, 
she was frustrated because her clay sculpt would 
change from day to day due to an uneven drying
even though it was being kept in a damp enclosure. 
Daily, she needed to re-wet it, 
manipulate it; 
or add wet slip to smooth out distortions.
Fawn said, "It would take at least three weeks of 
manipulation until the clay itself 
finally seemed to give up and the sculptor, 
at last, was in charge".

Safety note: Inhaled porcelain dust can be fatal over time. 
Protect your lungs when 
cleaning, sanding or direct sculpting porcelain!
Tiny detail in her small work was often applied with wet slip, 
to which white vinegar 
had been added to thicken it to a buildup consistency.
Note: Fawn Zeller used very little vinegar to thicken slip 
that she was applying to 
her sculpt in liquid form. Other artists needing larger
pieces of clay while working in more traditional additive 
processes might pour a bit 
of slip onto a plate of hard, dry plaster to draw excess water out.

"Pate sur Pate" Fawn Zeller discovered a technique 
called "Pate sur Pate" which 
changed the way she sculpted in porcelain forever.
Tiny detail in her small work was often applied with wet slip, 
to which white vinegar 
had been added to thicken it to a buildup consistency.
Note: Fawn Zeller used very little vinegar to thicken slip 
that she was applying to 
her sculpt in liquid form. Other artists needing larger pieces
of clay while working in more traditional additive processes 
might pour a bit of 
slip onto a plate of hard, dry plaster to draw excess water out.
Fawn started sculpting in the customary manner by manipulating 
porcelain clay in a moist, 
leather hard stage - always keeping it moist throughout 
the sculpting process but was 
frustrated by the difficulties of keeping her small 
sculpts consistently wet. 
After many years of work, she discovered a better way.

Fawn’s Discovery
In 1963, Fawn discovered a totally new approach 
to sculpting with porcelain clay. 
She was working on a project so very small that 
she needed to work
under a magnifying glass. The details were so small 
that a brush buildup seemed 
more effective, instead using a modeling tool.
She found that she couldn't keep this little head moist enough. 
Yet she noticed 
she could easily brush thinned slip onto the dry clay.
The drier the tiny head became, 
the better liquid slip adhered. This fresh clay 
could then be manipulated, 
modeled and carved into fine details and
smoothed with a brush."It was an exciting discovery. 
This extreme and opposite 
approach was a very different technique.
The completely dry sculpture can still be changed 
and even have added details. 
When my first attempt with this unusual method was
high fired to cone 6, and the result was beautifully fused, 
satin finish porcelain, 
I knew I had found a better way.
The revelation proved to be the most thrilling 
discovery of my doll-making career!"
quote from the book 
"Fawn Zeller's Porcelain Dollmaking Techniques" by Sybill McFadden

"The firm, partially fired clay almost 
grabbed at the unfired, very thinned 
porcelain slip being added for detail work. 
The model could still be carved away
and added onto, after wetting, 
with far better results than I had ever found
 possible when working with leather hard clay."
"The application of thinned slip onto the partially 
fired head is easily 
blended in place with a dampened brush or a toothpick
with cotton twisted on one end, dipped in water 
and the excess pressed out. 
It was found that a few drops of white vinegar
added to the brushing water helps 
keep the surface from crusting. 
The delicate contours achieved, 
after the first firing,
were done with a fine rasp-filing tool. 
The final clean up of the 
larger areas was made smooth with a 
No. 100 grit rubber scrubber.
After all traces of clay dust was brushed away, 
any remaining particles 
could be picked up with a slightly dampened sponge or chamois skin."
quote from the book 
"Fawn Zeller's Porcelain Dollmaking Techniques" by Sybill McFadden
Fawn's use of slip for sculpting is very similar 
to an expert's use of 
decorative "slip trailing" 
where liquid slip is drawn onto raw clay
from a squeeze bottle. 
The results can be stunning especially when the
 newly laid down slip is further shaped 
into more delicate designs by expert hands.

After discovering this new method, 
sculpting was an exciting adventure 
for Fawn. She proudly stated, 
"All the portrait museum dolls I did after 1963
[each an original] were created using this method".

Independent Discovery!
Fawn later found that her new technique, 
the "buildup of wet slip on dry biscuit
 for carving detail", was NOT a new technique.
After some research at the library, 
Fawn realized that she had independently 
discovered a technique which she thought 
was developed about
100 years before her time 
[actually the process is even older!] She explains, 
"Somehow in developing my doll making I, too,
came across this revolutionary process,
 without ever having heard or read 
of the technique."Surely an artist can start with raw clay and
hollow their sculpts by hand as Fawn did, 
but they can achieve a similar 
result that is completely ORIGINAL by starting from casts
made from molds with minimal detail - just basic shapes. 
This will provide 
a quick hollow starting point. 
Essentially it would be a hollow skeleton
from which to build upon. 
The casts could be removed from the molds before 
the leather hard stage 
to allow some quick reshaping but most of
the sculpting would actually 
only occur after it was already soft-fired.

I highly recommend the book 
"Fawn Zeller's Porcelain Dollmaking Techniques" 
by Sybill McFadden to anyone 
who wants to learn more about Fawn Zeller's work.
Porcelain Shrinks

Raw porcelain shrinks by at least 10% as 
it vitrifies in the high fire. 
A clay manufacturer should be able to 
give you an approximate rate of shrinkage.
It is very important for an original doll 
sculptor to know the shrinkage 
rate of their clay, especially if they are working in
a specific scale like 1:12 (doll house size). 
If your clay will shrink 10% 
then you must do the math so you can sculpt
at an appropriate larger size to insure 
your sculpt will shrink into the 
exact size you need.
The shrinkage rate may be noted somewhere 
on the product's packaging or 
on the manufacturer's web site.
If not, then it might be wise to set up a test. 
A test strip can be 
built up of clay insuring the strip is consistently
thick and consistently wide then cut to exactly 10". 
After firing, 
it is easy to calculate the rate of shrinkage
by comparing the new size to the original.
Once you find out the shrinkage rate then 
you can scale a set of 
reference photos or draw a set of figures in this
larger size as a guide to your sculpting.
Thickening Clay
The traditional way to thicken clay is to 
lay it on a block of plaster 
(a "plaster bat") to let the plaster 
draw some of the moisture away.
A flat area of any plaster mold will do 
but those who need thicken 
slip often, will take the time to make a 
special portable plaster bat
specifically for this use, rather than risk 
dropping their valuable plaster molds.
NEVER pour any contaminated water down 
your drains! Both plaster =&
 clay can clog your drains.

Here are some things you never knew that you could do 
with Porcelain in Miniature.
Direct sculpting can be started before the greenware is even leather hard!
While doll artists are taught to be EXTRA careful when handling greenware
 for larger dolls, miniature doll artists have found that
they can really abuse their greenware and get a startlingly good finished 
product! To keep greenware from splitting and cracking in the kiln,
you often have to prop larger pieces and handle the wet greenware 
VERY carefully ... this isn't a problem with miniatures (those dolls 7" and under).

They regularly take miniature hands, cut the fingers apart and reposition 
to articulate the hands before the greenware is even leather hard!!!
With a sharp scalpel (be careful), cut apart the fingers ... 
don't try to cut all at once, but gently score through.
Then, using a sable brush dipped in distilled water, you can refine 
the cut edges and even move the digits to make a pointed finger,
curled hand, fist, or anything that your heart desires. Set aside 
the greenware, let dry as usual, clean and fire to bisque!
The same method can also be used to reposition heads!!! Experiment!!!

Fawn Zeller explained why she chose to sculpt directly in porcelain clay: 
"the end result remained my original sculpture and fired more sharply,
defined in every detail."
Porcelain Slip

With many personal trials and tests, it was discovered that dried porcelain slip makes useful modeling clay. The white scrap trimmings from pourings, when rolled out to a powder, should have just enough drops of glycerin added to make it the right consistency. This plastic mixture is good for fancy trim, preferably already colored; it can be stored in a dry glass container. It will never dry out. It is always ready for rolling to cut ribbons, floral or fruit decorations, and to be squeezed through a disk extrusion tool.

It may be placed on unfired greenware with slip, and onto partially fired bisque with thinned slip and a drop of matte glaze underneath. The glycerin clay items should be added at the very last so as not to accidentally disturb the [decorative]design which does not harden or set up because of its oil content. The clay will, however, hold its shape equally, with whatever else is applied in various buildups on the porcelain piece.

It has one disadvantage, however, a disagreeable odor and smoke when being fired in the kiln. Therefore, it needs plenty of ventilation. The end result has always been worth this brief unpleasant period.

quote from the book “Fawn Zeller’s Porcelain Dollmaking Techniques” by Sybill McFadden
Lace draping
Lace draping is where thin 100% cotton lace is soaked in slip and after all excess slip has dripped away; it is then applied onto a raw clay item. The lace is carefully pushed and pulled into place to achieve a natural look. The cotton will burn off in the kiln leaving only a fragile 3D impression of porcelain lace.

An example of lace draping: an artist might drape this porcelain laden lace around the brim of a sculpted bonnet or against a sculpted bodice.

Making a head and shoulders for doll
Porcelain for handsculpting has been used for centuries 
by ceramists in sculpting their "objets d'arts". 
I use the German brand "Hutschenreuter" or
the French brand "Limoges" and fire it only once on 1220 or 1240 degrees Celsius.
 I paint the porcelain with watercolour and I cover this with a
varnish as a protection.

To start with the head, I take a styrofoam egg and put a pin in 
the pointed side (so I can recognize it once it has been covered).
I grease the egg with salad oil and cover it with two flat slices of porcelain (ill. 1).

Then I start modelling the chin - the side of the pin (that can be removed now). 
You can model the face including the ears as you are used to, 
keeping the head in your hands.

If you are working very slow or if you do have dry and warm hands 
I would advice to put a piece of plastic foil (plastic wrap) between 
your hands and the head. If you don't the back of the head will dry, 
shrink and crack. If you keep the head wet, then you can work on it 
for about two weeks.

When you have finished sculpting the head, you let it dry for one to three hours. 
It has to reach a certain stage between wet and dry. Then you will be able to 
open it to remove the egg. The egg cannot be left inside because the porcelain 
will shrink while drying (See below for further instructions).

To give the head a neck and shoulderplate I have developed a special stand (ill. 2). 
I can put plastic tubes of different lengths on top so that I can quickly adjust 
this stand to fit the size of the head and the length of the neck (ill. 3). 
Cover the stand with plastic foil (plastic wrap) and prepare the shoulderplate (ill. 2).

Now we can operate on the head to remove the egg, remove excess material and 
prepare the neck. First we will make a hole for the neck by removing a round 
piece of material with a little knife. Then remove the top of the head - 
the brain pan- as you do with a boiled egg. Don't forget to place a reference 
mark on each piece so you will know how to put it back together (ill. 4).

You can push out the egg now with your thumb (ill. 5) and remove some of 
the material on the thickest parts of the head, for instance the forhead 
and the chin. You can use the tool showed on ill. 5.

To replace the top of the head you have to make scratches -using a little knife- 
in the two parts that have to be joined. After scratching you will have to wet 
these parts with a wet brush and without removing the scratches. Now press 
the top of the head on the right place aligning the two pieces where you 
have put the reference marks before. Smooth away the seam.

Put the head on the stand in the position that you prefer (ill. 2).
 Model the neck out of a slice of porcelain and smooth away the seams.

Now cover the head with plastic without closing it entirely. 
Leave it this way for a few hours so the moisture can spread evenly.

If the entire piece feels the same (as the head before operating) 
you can remove it from the stand and work on the inside of 
the head if necessary.

Let it dry slowly before firing.
Support during firing tips: by Lauren
I use either alumina hydrate or silica sand sifted onto the shelf 
first to allow the pieces to slide as they shrink and also 
to protect the shelf. 
Then I use a product called “prop” which comes in either a blanket 
or as something similar to pieces of fluffy wool to support pieces 
that might slump or bend.
 It is a little tricky but not that hard. Always allow some leeway 
for the shrinkage of the porcelain when you prop ie use fluffy 
pieces that can compress 
easily. I lay the carousel figures on their sides and put a little
 bit of the loose prop under the legs that are on the top side 
or in any other place that 
needs some support. You can roll pieces of the blanket prop up 
and put in large openings to help hold them up. I have not used 
it for bowls etc. yet. 
All of these products can be reused over and over. Sift the sand 
or alumina hydrate back into a container. Don’t use both together though. 
I recall having to fire the A.H. before using it the first time 
but I have been able to use it over and over. Look in doll
 making supplies for the prop.

2 responses

  1. Kathy

    I can’t read the interesting info because it spills over to the right margin. Do you realize this? Please fix. Thanks.

    September 16, 2012 at 2:29 PM

  2. katdazzle

    I think I fixed it all to be readable now. Thank you for drawing it to my attention.

    September 16, 2012 at 6:08 PM

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