Oooops. One Bad One

After everything cured until Monday, I started to make test castings. Just to make sure that the molds were good. All of the texture was picked up and the detail was there.

I have one bad mold.

I will spend some time to see if I can save it. Then make another test cast.

If not good, I will have to start over and make the new mold.

Step 2B

 

 

 

All of the coats of rubber mold have been applied and next I mix up and apply the hard plaster shell. Both of these the rubber mold and the plaster shell make up the "Mother Mold"

 

With the Mother Mold, I then cast all of my pieces. This mold should stand up to about 500 resin castings before I have to make another. Because of the rubber I use, I can use this mold for lost wax bronze casting, metal castings like aluminum, steel, gold, silver and of course plaster. Very versatile.

 

I have poured the hard shells, wait 90 mins. then I an de-mold the pieces. Separate the hard shell from the rubber mold and separate the rubber mold from the original clay piece. Very carefully so I don't damage the original.

 

Everything cures until Monday when I pour a test casting in plaster to see if the molds are good. If not, I start all over.

 

Step 2 - Mix and Pour and Wait and Mix and Pour and Wait

 Now I start the rubber mold making.

First I mix the two mold chemicals together in equal parts, and I now have 8-10 mins to paint it on the clay original before it becomes too thick.

 

 

 

This is the first coat of six. It is important to smear the rubber over the entire surface and with the brush ...  scrub it over every surface, and into every crack and crevice. This first coat picks up every little mark, and in my case fingerprints. This sets the surface texture of the final casting. 

If this coat does not set correctly, I will have to start over but I wont know until the entire mold is done, the ceramic shell is made and I cast my test piece.

Now I wait 90 mins. and add the second coat, wait 90 mins. next coat, etc. until all six coats are done. 

I am doing a single piece first just to get the timing correct with the mixing and coating times, as it is all according to room temp. and humidity. 

Note to other sculptors
No one told me when I was in high school that I should pay more attention in chemistry and geometry and physics classes because as a sculptor I would need to know what chemicals to mix for the molds, castings ... what chemicals to use and in what amount for color patinas and timing of the coats ... how much clay, metal and foam I will need for a piece based on size and shape ... for large sculptures indoors weight of the piece based on lbs./cu foot of the materials bronze vs. marble vs. granite... and the load limit of the floors it is sitting on ... outdoors I need to be aware of temperature extremes to determine which patina chemicals to use ... wind directions and speeds in a normal year for how much torque the sculpture will take and where and how many holes I need to have for the wind to go through ... if in a rainy and snowy environment I can't have areas where the water or snow will collect but will run off...

Tomorrow I will do the other two sculptures together if this one works out well.

And Now Making The Molds - Step 1

 

 First step in making the molds is actually reworking the original clay pieces, filling in all of the holes and cleaning up the undercuts. All of which makes it easier to cast the final piece. This part of it took me almost 3 days, but it will save me a lot of time and trouble later.

Next I make a box around the pieces to hold the rubber mold and the plaster shell. I am dealing with liquids, which means of there is a hole in my box, the mold materials will leak. Not a pretty site, very messy and a lot of work to clean up.

The mold material is plastic when it dries, so I can use cardboard as my box as the plastic will not stick. Below are the chemicals I use to make the rubber molds (top row), the plaster shell (boxes) and the bronze cold castings (the jugs). Each is a combination of mixing two chemicals together. Temp. and humidity is critical +- 5degrees. 

I had to postpone my first round of making molds because the smoke from the forest fires around us made it impossible for me to open the windows for ventilation. So today I can work.