Shrink or Enlarge Your Medals or Sculptures

By Lindley Briggs

Industrial Polymers Corporation has two remarkable products that I have been using for a number of years that I am very excited about. HyrdoSpan 100 enlarges the size of a scuplted original up to 60 percent; HydroSpan 400 reduces the size of a sculpted original up to 56 percent when you pour it into your original mold and allow it to shrink/cure for several weeks. A food dehydrator greatly speeds up the shrinking/curing process.

This is an inexpensive method of reducing medallions and reliefs to a smaller size. The reduction process can be repeated numerous times, requiring a new mold of each reduction. I have shrunk a 15-inch diameter medallion down to a 3-inch diameter medallion in four steps. (See ‘Celestial Encounter’) The detail is totally amazing! All you need is time. Having the ability to make your own molds makes the process even less expensive.


The most important tips when using the HydroSpan 400 include making sure the water is as COLD as you can possibly get it without freezing it. You only have around two minutes to mix and pour the four parts water to one part HydroSpan 400 into your mold. The COLD helps slow the set up time. After you spray the your mold release (I use Polytek 2300) into your rubber mold (if it is not a silicone mold), wait overnight to make sure the release is totally dry. Otherwise, you will get a myriad of tiny air bubble holes in your final cast. Clearly, using silicone molds is preferable, but we always are well stocked with Polytek 74-30 polyurethane rubber in our studio. Some adventurous artists pull a vacuum on the HydroSpan 400 after it is mixed with water to eliminate all air bubbles in the final cast. That is a daunting feat since the pot life of Hydro- Span 400 is so incredibly short. With a little extra effort – and a lot of trepidation – I managed to shrink one of my husband Jeff’s 24.25-inch by 23.75-inch by 1.75- inch plaster reliefs by 50 percent.

This required a very large volume of the liquid to thoroughly mix and pour into the mold within two minutes! It came out perfectly (phew!). When your sculpture is fully cured/shrunk, you have a floppy, amber colored, rubber original that will require a new mold for a hard positive cast. HydroSpan 100 enlarges a sculpted original up by 60 percent. You pour the two-to-one ratio A and B components into your mold, after spraying it with mold release. After it sets up in around one half hour, you take it out of the mold. Next, you totally immerse it in a tub of water for several weeks, making sure it stays immersed at all times. The process of the expansion over the two-week period is often visually bizarre as thinner sections expand quickly and twist and turn into weird contortions. Sometimes I cut a slit into the back the thicker sections to facilitate the expansion process.

The end result is a blue, gelatinous, wet enlargement of your original. I have had the best results in making a mold of this by tacking it to a prepared board and making a plaster waste mold. The holes from the tacks and any other imperfections can be repaired in the plaster mold as well as in the final cast. The details on the enlargement are not as perfect as with the reductions, which is only logical. The picture of my two ‘Classical Profiles’ (above, left) shows a current work-in-progress. The original profile is on the right and the plaster enlargement is on the left, surrounded by a clay wall in preparation for pouring a polyurethane mold.

Over the past eight years or so, I have reduced a number of smaller 3-D sculptures (see the two ‘The Perfect Men’ bronzes above) as well as many relief sculptures and medallions. It is fascinating to observe how a shift in scale can so radically alter the impact of a sculpture. It also can radically change the venue in which a sculpture can be exhibited and sold. The IPC website is: ( There are some informative instructional videos on the website about both types of HydroSpan.