Catching Up Part 1: Mold-making

With the flurry of activity and craziness leading up to my departure for Colorado I never had a spare minute to sit down and do a proper update here and for that I apologize.

I am finally back in the office today and have nearly 1,000 photos and videos to go through. I will pick a few of the best that illustrate the process and share them over several updates.

The shims and interlocking keys have been added so that
everything will line up when the molds are finished

I used a soft urethane rubber to make all of the molds on this project. Since the project is a "one off", meaning that we would be casting only one, the rubber I chose does not have a long shelf life and will eventually revert back to liquid in 3 - 5 years.

Mold keys are held in place with sewing pins so they don't shift as they set up.

The rubber is built up in many layers to a thickness of approximately 1/4".

Multiple pieces in various stages of molding.
 

Mold-making is tricky business and as I've grown older, one of my least favorite aspects of this line of work. There are so many things to consider when making molds that it can become overwhelming at times: thickness, undercuts, pourability, etc. It's all a bit nerve-racking and if I miscalculate one little thing it can have a domino effect and lead to horrible results. The rubber comes in three parts: the base, the catalyst and the thixotropic or thickener. All parts must be carefully weighed on a triple beam balance to within the tenth of the gram; one miscalculation and that batch of rubber is ruined. All of the parts must then be mixed by hand for a pre-determined period of time. It's a terrible feeling when something goes wrong but I have learned to keep copious notes at each step so if something happens I can quickly isolate and correct the problem. I was very fortunate that all of the rubber molds for the Waterbearer came out perfectly.