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Mississippi Valley Archaeology Center




Making Stone Tool Replicas

Projectile points including one replica

Which do you think is the real artifact?  

Click here for answer.

Archaeologists often find artifacts, or objects made by humans, that are one-of-a-kinds.  Unique artifacts give credit to human creativity, but can make an archaeologist's job difficult in several ways.

Obviously, it would be hard for an archaeologist to study a tool if it was in a museum 300 miles away.  And even if the artifact was close-by, the risk of altering or damaging the artifact may be too great to allow for study.  Some private collectors also do not allow studies to be done because of risk factors.  Even when examination is acceptable, few people would feel comfortable working with artifacts such as those seen below.

Replica artifacts
Replica Artifacts

In cases of rare or fragile artifacts, making replicas can create several advantages.  Replicas can be examined by archaeologists for select information, can be more easily displayed and transported, are less likely to be stolen, and can be used repeatedly in educational classes and activities.

For these reasons, a method for creating replicas of stone tools has been developed, largely through trial and error.  The technique used by the Mississippi Valley Archaeology Center was developed with the guidance of Betty Steele.


The Process

  • Step 1

The mold

The artifact is embedded in clay so that only one side is exposed.  The edges are carefully worked so that when a cast is made, the two halves of the mold match perfectly.  Once the artifact is properly embedded, liquid rubber mixed with a hardening agent is poured on.  The artifact itself is not harmed or altered by the mold materials used.  

The mold
The rubber hardens in about 48 hours.  After that time, the clay is broken away, leaving the mold and stone artifact.  Then the other half of the mold is created following the same steps.  Once complete, the two halves are coated with a lubricant so that the mold can later be removed without injuring the finished replica, or cast.
  • Step 2

Mixing the resin
With the two halves of the mold ready, the next step is mixing the plastic resin that will form the replica artifact.  The resin is made from two ingredients.  The Part A and Part B ingredients are mixed together in specified amounts to make the resin.
  • Step 3

Adding pigments
Part of mixing the resin is choosing the color of the replica, which can be made to resemble the original artifact or be altered to better highlight aspects of the artifact or easily distinguish it as a replica.  To do this, color pigments are added to the resin.
  • Step 4

Getting out bubbles in the resin
The ingredients are mixed together using a jewelry vibrator.  After mixing, the resin is allowed to sit so that air bubbles can escape.
  • Step 5

Two mold halves are put together
Next, the resin is poured into the two coated halves of the rubber mold.  Soon the resin begins to thicken and the two mold halves are put together.  The edges are sealed with nails and the top is weighted down for an extra tight seal.
  • Step 6

An incomplete replica
An Incomplete Replica

After about 8 hours the resin has hardened and the mold can be opened, revealing the cast.  The resulting replica may indicate that the molds were not precise or the seals were out of alignment.  Certain steps of the process may have to be attempted again.


The Finished Product

The finished product

Eventually, or perhaps the first time, the end result is a replica that is exactly what is wanted.  The real artifact can then be returned to safer storage or display while the replica can be freely used for education, research, and display.

Answer: The real point is second from the left.

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Mississippi Valley Archaeology Center at the University of Wisconsin - La Crosse
1725 State Street, La Crosse, Wisconsin 54601 U.S.A.
Phone:  608-785-8463, Webmaster

All material Copyright 2000-2014 Mississippi Valley Archaeology Center at the University of Wisconsin - La Crosse

*MVAC Educational Programs are supported in part by the National Endowment for the Humanities.  Any views, findings, conclusions or recommendations expressed in these programs do not necessarily represent those of the National Endowment for the Humanities.
*This project was supported, in part, by the National Science Foundation.  Opinions expressed are those of the authors and not necessarily those of the Foundation.