I am a granite fabricator and a few years ago had a client call me to say his brand new Kohler cast iron sink had popped all the enamel off the top of the hump seperating the two bowls. I couldn’t offer him an explanation why it occurred and never heard back.
My grandma’s 80 yr old cast iron sink did the same thing but the sink base cabinet had rotted on one side and I assumed the lack of support allowed the sink to try and bend causing the porcelain glaze to pop off the hump between the bowls.
Today I had my helper try to revive an old wall hung cast iron sink I wanted to use in my bathroom and he was doing a great job of polishing it up with a 200 grit diamond pad followed by automotive rubbing compound.
He was getting a beautiful mirror like shine on the porcelain and then all of a sudden the porcelain developed a spiderweb of cracks and popped about 1″ by 3″ of porcelain loose. I assumed it had heated up and caused localized expansion. He maintained very little heat was building up so I don’t know what else to attribute it to.
My only theory is that a highly polished surface has more surface tension? and is therefore more likely to crack. I don’t really understand the physics behind it but I have heard that highly stressed metal components are shot peened to relieve surface tension and discourage crack development.
This is the best guess I have but it still doesn’t explain the first two failures.
Any ideas?
Karl
Replies
interesting observation, I always thought it was dissimilar materials and co-efficients of expansion .. especially at the bridge between sinks, when one side is full of hot water and the other empty .. I think it was probably overheating from the prolonged buffing too .. but at last I have a reason not to clean the sink .. look forward to seeing other theories ..
"but at last I have a reason not to clean the sink"My sentiments exactly. The polishing was looking so good I was going to have him do the clawfoot tub next. At this point any thoughts I have of cleaning and polishing the 90 yr old tub are history.Karl
You have any thoughts on why this might have happened?