Just hold the bong with rubber gloves or smth, glass becomes very slippery when slick with iso/salt mixture. I'll never forget my beautiful week-old (very pricey) bong positively exploding into hundreds of tiny pieces after slipping just an inch out of my grip and tapping a porcelain sink when I was shaking it clean for all of the friends I invited over to try it. Was over 10 years ago but I remember it like it was earlier this afternoon. :/