Just PB/Sn ROSIN so it would stick.
No the waterblock is just one I made
should have seen the original waterblock it was made out of a metal called Ampco90. I believe it is a berilium copper mix. I took it in to be machined and the guy says. Oh yea that's Ampco brass should only take about an hour=$65 dollars. Calls me up and says it took him all day (this stuf is real gummy) But he was only going to charge me $250. GFY. you would think he would have called and said hey this stuff is tough to cut.