Have you ever wondered about the mold making process???   What steps go into those tiny pieces of plaster that allow you to make beautiful miniature dolls?  How does an artist get from a clay sculpture to hundreds, or even thousands of production molds available for retail sale?  Why do some molds last seemingly forever and others wear out after only a few pours?

In this demonstration, it is not our intention to try to teach you mold making, but to teach you ABOUT moldmaking.  We will show you the steps, start to finish that go into making a highly detailed, high quality plaster mold, and how to turn one sculpture into hundreds of molds.  


Meet Nicholas.  He is sculpted in oil base (a.k.a. "green") clay.  I am hoping that he will make a good Santa, Father Christmas, shopkeeper, bartender, lamplighter, pirate, etc. ect. Kind of a man for all seasons.

Using oil base clay has it's good and bad points.  It is well suited for miniatures, since it will not dry out, so no chance of a nose flaking off as with water base clay.   Because there is no drying, there is also no shrinkage.  On the other hand, it is difficult to get a mirror smooth surface in, which is easier obtained with some other products.  

But it is what I am used to working in, so this is what Nicholas has been modeled in.

Fortunately, this is as far as I have to go.  Larrell now has the task of turning a single casting into dozens of production molds.  He will take it from here.....

The clay model has been sealed, and the first step in the mold making process is just beginning.

The parting line must be determined, and the piece is then "clayed up" using water base clay.  This means that a base is built beneath and around the model up to the exact parting line which will determine the two halves of the final mold.  Finding the correct parting line is essential.  A mistake can mean undercuts that will prevent a casting from ever being pulled properly from the finished mold.

When the claying up process is completed, the model and clay are soaped,  mold boards are clamped into place.  Notice that the clay bed that the head rests in is smoothly contoured. 
Grade A pottery plaster is carefully weighed and mixed, and poured into the mold form.  

When the plaster is set, the boards are removed, and the water base clay removed.  

 

The first half of the mold, with the sculpture still in place is then placed back into the mold boards, the surfaces prepared, and the second half of the mold is then poured.

When both halves have completely cured, the casting is removed, and the mold is allowed to dry completely. 

This initial mold is sometimes referred to as a "waste" mold, although I can not imagine why.  Our waste molds are made with care and precision, and the castings from these initial molds are of very high detail with minimal seam lines.  Perhaps the term waste mold refers to the fact that if we intend to we will further refine our molds, proceeding to a master mold and rubber cases, this first mold will  eventually  be discarded.

Because my sculpture was in oil base clay, and I still have lots of detailing that I want to do, from the initial mold, a wax model is cast.  

The wax used is well suited to fine detailing, and to refining the overall surface of the piece to a perfectly smooth surface.  Any minor changes that are desired can also be made at this point.  

Working with this wax model  gives me an opportunity to perfect the piece without fear of accidentally removing detail, etc.

From the refined wax model, a second mold is made.  This mold is called the "Master" mold.  All surfaces of this mold are as smooth and refined as possible, and all seam lines are tight.

Because of the extra work done on the wax model, the detailing in the Master Mold is very sharp and defined.

The master mold is test cast several times to make sure that it pours and drains well, and that the casting is sharp and pulls from the mold easily.  Nicholas is such a happy guy, he nearly leaps out from the mold!
The master molds are prepared, and then a polyurethane material is poured over them to create a rubber case.  The rubber case or rubber master is what is used to produce many duplications of my mold so that I can offer Nicholas for sale as a mold.

 

This is the completed  rubber case. The inner surface of the rubber master is a reverse image of what the inside of the mold will look like. It will be used to mass produce molds for resale.  These molds are referred to as "production molds".  The rubber exactly duplicates all detail in the molds, and if used and cared for properly, can produce hundreds and sometimes even thousands of molds.

 

The rubber cases are filled with properly mixed grade 1 pottery plaster.  Molds are allowed to cure while in the rubber case.Molds are removed, edges trimmed, and carefully inspected for any pinholes or flaws.  Molds with flaws of any kind on the casting surface are discarded. 

 

Molds are removed, edges trimmed, and carefully inspected for any pinholes or flaws.  Molds with flaws of any kind on the casting surface are discarded. 

Several production molds can be made per day from a rubber case.

 

A lot of care and expertise has gone into creating your miniature molds.  Proper use and care on your part will help keep them producing clean sharp castings for a long time.

Molds should be completely dry before initial use, and always tightly banded when cast.

Use the softest brush to remove any dust or dried porcelain from the interior of your mold.  Stiff bristled brushes can scratch the surfaces, resulting in damaged castings. 

Do not use sharp objects to remove porcelain from the inside of the mold, as the plaster will scratch easily.  

Do not over-pour your molds.  Pouring molds to the point that they are very wet (many consecutive castings in a day) will quickly wear out the fine details in your mold.  Instead, cast 2-3 times, and let the mold dry before recasting.  

Take the time to clean up even the outside of your molds before storing them.  It is so much nicer to pour a clean mold than one with old dirty slip all over it!

Always store molds tightly banded together to prevent chipping or other damage.  A small piece of cardboard over the pour holes, or storing pour hole side down on a clean shelf will prevent dust on the inside of your molds.

We hope that you have enjoyed learning about the many steps that have gone into creating your miniature doll molds!  If you would like information regarding production of molds from your own sculptures, please email us for further information and a price estimate.  We offer any and all of the steps shown in this demonstration, as well as manufacture and drop shipment of production molds.  We look forward to filling your mold making needs.