Creation of the ceramic shell that surrounds the wax in lost-wax casting involves the mixing of colloidal silica (powdered silica suspended in distilled water) with fine silica sand to produce a slurry into which the wax pattern is dipped. Dry silica sand is then dusted onto the wet surface and the assembly is allowed to dry.
This process is repeated several times until a coating is built up around the wax pattern. When the desired thickness is reached, the assembly is placed into a “burn-out furnace”, where two things occur: The wax pattern melts and runs out of the shell, and the heat “vitrifies” the silica assembly into a fused, hard ceramic shell.
It is into this ceramic shell that the molten metal is poured to produce the desired metal casting.
Years into this process, the manufacturer of the colloidal silica introduced a new innovation – a dye was added that gave the shell a yellow color while it was still damp, but gradually turned orange when it dried. This was a valuable addition, as it allowed us to speed up the investment process since we were now no longer unsure whether the previous coat was dry before we applied the next coat.
In the room where this investment process took place, we kept a 5-gallon bucket of water where we would rinse our hands after investing the wax pattern. For years we emptied this bucket out on the ground on a corner of the property, and rinsed the bucket out before returning it to the shell room.
Now to the story:
One day, as I was rinsing out the bucket, I was approached by a U.S. Marshall who was looking for a fugitive that he believed either was working for us now or had worked for us in the past. I looked at the name and photograph and description of the fugitive and asserted that I had never seen the individual, that he was not working for us now, and that he had not ever worked for us.
The Marshall clearly did not believe me, and he requested to be allowed to come into the shop. I invited him in, and he looked over our employees and asked several of them if they knew or had ever seen the man in the photo. None did or had.
The Marshall departed, obviously frustrated, and apparently believing we were covering for the fugitive.
Several weeks later I was at home having dinner when I got a phone call from a friend who owned a business at the end of our street. He suggested that I might want to come back to work, as there were a number of emergency vehicles, including a fire truck, on the street in front of the foundry.
When I arrived at our street I found the Sheriff’s Department had set up roadblocks at both ends of the street and was denying access to any of the buildings on the block. I identified myself to a deputy as the owner of the building where the emergency vehicles were parked and asked to be allowed to pass. A short time later I was granted access.
When I arrived at the front of the foundry I was surprised to find not only the fire engine that could be seen from the end of the street, but a second, smaller fire truck, a fire chief’s pickup truck, a Hazardous Materials truck with two people in HazMat suits including breathing units, two Emergency Medical Technicians, and several firemen. Most of the vehicles had their red emergency lights on and rotating, and their headlights and spotlights focused on the corner area where we routinely washed out our 5-gallon bucket.
The lead fireman had directed the deputy to let me through, and he greeted me as I arrived. “What the hell is that?” He pointed to the wash area.
One feature of the dye used in the colloidal silica is that not only does the yellow color turn orange as it dries, and white after it is subjected to heat, but it also reconstitutes to yellow when subjected to water.
We had had a light rain that day, and our dumping ground looked pretty formidable – a slightly muddy, ugly mixture of yellow, orange, and white.
I explained what it was and asserted that it was totally inert and safe. He was having none of it.
I asked permission to enter the building to retrieve the Material Safety Data Sheet provided by the manufacturer, that would give a complete description of the colloidal silica that was causing so much angst. He hesitated, then made a call on his radio. It was then that I realized they had set up a remote staging area on a vacant property a couple of blocks away.
It took a while, but I was allowed to enter the building. I returned with the MSDS and gave it to the fireman. He read it over, then gave it to another fireman to deliver to whoever was in charge at the staging area.
Time passed. Apparently from the staging area a number of calls were made, to the emergency number listed on the MSDS, and several other CTA calls to verify the information.
Eventually the radio message came from the staging area. “Wrap it up. The material is inert.”
As the assembled team began to stand down, I asked, “What would you have done if I hadn’t arrived?”
“We would have brought in an excavator, dug out the soil, loaded it into sealable 55-gallon drums, and transported it to a hazardous waste materials site.”
“Who would have paid for that?”
“You would.”
Peggy Detmers says
MAN!!! Would that upset US Marshall set that up? Wow!