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How to Make a Great Mold, Part 1
By David E. Parvin, A.L.I.
ave ten different mold makers over the model leaving a narrow gap
each make a mold of the same into which the rubber is poured. Here
object and you will get ten is where it can get confusing, a block
molds which vary in design, mold is a pour mold while a skin
materials, and function. All might be mold may or may not be. Remember
satisfactory though you likely would Logic 101:
be able to rate them from best to If A = B and B may or may not = C,
worst. This is the first of two articles then
in which, while I don’t claim to have 1. A = C.
all the answers, I will explain how to 2. A may or may not = C.
make a really great mold. 3. It’s Tuesday.
The absolutely most important 4. All of the above.
requirement for a mold is that it #1. The model, a mother’s hand holding (For more information on skin and
produces perfect reproductions her baby's foot. block molds, see “How to Make a
capturing all detail without flaws or Secondary Mold,” SJ, July 2004,
noticeable parting lines. There are “Secondary Molds in Life Casting,
other considerations such as Part II”, SJ, November and
durability and ease of opening and December, 2004, all by D.P. If you
closing. In addition to filling these can not locate your leather bound
requirements, the mold that I will archival copies of Sculpture Journal,
describe will allow one easily to contact Jon, the editor, who will
make a new mold if the edition is so happily e-mail the articles to you. Or,
large that the first mold wears out. I will gladly do the same.)
Just so that we are all on the In this article, I will describe
same page, let me define a few things how to make a really slick skin mold
even though most readers may using the pour, not to be confused
already know them. First, the object with “poor” or “pore,” method. Since
of which the mold is made is not I generally write on life casting, I
called the original, it is the model. will mold a mother’s hand holding
Next, the names commonly used for her infant’s foot. But, the model
the different types of molds may #2. The base with holes to fasten the could have been anything. And while
vary, overlap, or be ambiguous. The model and the inserts. the hand and foot is relatively small,
two most common types of molds about 6” tall, I have used this type of
used by sculptors are block and skin. mold for models up to several feet in
The simplest of these to construct is height. For even larger models, life
the block mold; just surround the castings or not, I would probably
model with a box, cup, etc., which is paint on the rubber. It’s going to
called the mother mold, and pour in seem that this process is pretty
rubber. After the rubber has set up, complicated with many little steps,
remove the mother mold, cut open and this is true. However, there are
the rubber, take out the model, and only six major steps:
the block mold is finished. Block 1. Attaching the model to the base.
molds are quick and simple to #3. A metal insert. 2. Covering the model with clay.
construct. But while they save time, 3. Building the mother mold.
they usually require more rubber and 4. Pouring in the rubber.
to some the cost of the rubber may be 5. Finishing the mold.
more important than the cost of 6. Using the mold.
labor. Also, the relatively thick If as you read along something
rubber may make it difficult to doesn’t make any sense, I would
remove delicate castings. suggest that you keep reading and a
With a skin mold, the rubber is few steps later it may become clear.
generally much thinner, more like
“skin.” This is achieved by painting Attaching the Mold to the Base
the rubber on the model and Photograph #1 shows the plaster
constructing a tightly fitting mother model. Note the line drawn on the
mold over the rubber. Or another #4. The metal inserts attached to the base. model which will serve as a guide to
way is to construct the mother mold
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