The key to using our Castaldo No Shrink Pink® jewelry molding rubber is precise temperature control. Our White Label® & Gold Label® rubbers are very forgiving and will work at a wide range of temperatures. No Shrink Pink demands precision.
Most jewelry vulcanizers are out of calibration or out of repair most of the time and rely on the forgiving nature of our other products.
Sometimes the top plate is hotter than the bottom; sometimes the right side is colder than the left side.
The only way to find out is to calibrate your vulcanizer with a good thermometer. Use the following technique .
Place a small block of wood -- about 1/4" to 1/2" (6 to 12 mm) thick--- as a cheap and easy insulator-- on the bottom plate of the vulcanizer after it has heated up for a while. Place the probe of the thermometer on top of it and close the vulcanizer plates gently. Go about your normal business and check the thermometer once in a while, noting the readings. After a few hours, repeat the process, this time with the thermometer under the block of wood.
This way you are isolating the two plates and not measuring the average of the two. It's like the old story of the man with one foot in a bucket of ice water and one foot in a bucket of boiling water-- on average, he's comfortable.
Once you really KNOW what the temperature is, make a test at 310 F /154 C, measure the results and increase the temperature one or two degrees. Repeat as needed.
Please be sure to always make your measurements the same way or you will not really be doing anything useful. If you measure your wax 5 minutes after it was injected, then do exactly that for all the tests.
Since wax shrinks a lot in the first five minutes, a little less in the second five minutes and so on for DAYS, it's best to wait as long as you can before measuring. Certainly 1 hour.
See also: Using No Shrink Pink.