Why You Need A Secondary Mold?

A mold that accurately reproduces the shape and details of a model can be used for rubber or resin casting, as needed. In fact, depending on the type of mold and the casting process used, a mold can be used over and over to make multiple casts of the same object.

casting resin types

However, every mold comes with a finite use life. It may end up deformed, tarnished or even cracked and broken after repetitive use. Would you then go back to making a mold of the object all over again? In case of a life cast, does it make sense to go to the trouble of making a body mold again and again? 

Anticipating such scenarios, experienced mold makers prefer to make a secondary mold before starting the casting itself. This copy can be used to continue with the casting even when the original one is spoiled or damaged. Moreover, it is possible to vary the material for making the secondary mold – like choosing polyurethanes or rubbers - thus extending the life of temporary alginate molds and the like.

Secondary molds bring another benefit into play. If the original mold has minor faults like bubbles, wrinkles or spots, the secondary mold opens up the possibility of correcting the flaws by improvising on the original piece. In fact, a mold maker can make one secondary mold after another till all the defects are corrected and the mold becomes perfect in every sense.

Therefore, mold makers are always advised to make a secondary mold just to be on the safe side at least.

You can source all your mold making and casting requirements easily online from www.artmolds.com.

Vacuum Chamber: A Must For Deairing

I use a variety of resins for my casting works. Most of my resins have a propensity to trap air and I regularly place the mold with the resin in a pressure pot. This removes all the air from the material and makes it disappear. As I let the cast cure in the pot itself, I get a perfectly bubble-free casting.

However, when I moved to making rubber casts, the bubbles seemed to return once I removed the rubber from the pressure pot. After several failed attempts, I gave up and bought a vacuum pump with vacuum chamber from artmolds.com.

Actually I had called up my regular supplier at EnvironMolds, LLC to discuss the issue first. He told me that a pressure pot does not work as effectively for soft casting materials like rubbers, especially silicones.

The suggested vacuum pump with vacuum chamber was reasonably priced and very easy to operate too. All I had to do was mix the rubber and pour it into a large container. The container should be big enough to accommodate four times the amount of rubber I wish to vacuum, as the rubber expands under a vacuum.

Simply switching on the machine initiates the vacuum process that removes all the air from the rubber. All it takes is a few minutes and the air is eliminated, never to return. I leave the container in the chamber for some time and later open the plate slowly to allow a gradual introduction of air.

As an added precaution, I place the mold box with the casting rubber in the vacuum chamber once again. The vacuum pump works its magic and the material easily flows into the tiniest grooves and undercuts of the mold. My casting turns out flawlessly without any sign of the slightest of bubble.

I seriously recommend that every mold maker or casting artist should own a vacuum chamber irrespective of whether they work with rubbers or not!