As a reminder (see last post) after mixing slip at our location since 1958, recently I was unable to achieve a functioning balance between specific gravity and viscosity. To put it in easy to understand terms. specific gravity is the measure of the water content of the slip and viscosity is the measure of resistance to fluidity. A low specific gravity means there is a high content of water. A low viscosity means that the mixture is very fluid. I was getting an extremely low specific gravity reading such as I have never seen before and an extremely high viscosity. That is like putting enough liquid into a batter to make it like a soup but instead it is like cookie dough. Neither low specific gravity or high viscosity are functional in a ceramic casting slip.
After three different batches of slip were attempted, all getting the same result, I started looking at the water supply. A consultant came over and dumped an extremely large amount of darvan. into the mix to achieve a decent viscosity but having no effect on the specific gravity. He claimed it must be caused by bad darvan from our source so I ordered a new supply of darvan from another source. According to his theory, I should have been able to add the normal amount of darvan to a batch and the viscosity would be solved. That didn't happen.
Then I mixed a small test batch of casting slip from scratch using a different water supply.The result is a perfect casting slip.
In the meantime I had called the water district which sent someone over to test the water. The results of the test was normal and I was told the problem is with my product. However my product is perfect when mixed with a different water supply It was impossible to get anything close to normal using the Boothbay water supply, which I understand is coming from Knickerbocker Lake in the summer. I will report my results to the Water District and the Town Managers of Boothbay and Boothbay Harbor. They can seek to understand this abnormality in the behavior of our water supply or not.