I was racking my brains to clean my bong after months of build up and I even bought some bong cleaner which was absoluttely useless. So I tried these wipes called Big Industrial Wipes. Its excellent at removing all that really hard to get off tar from the down pipe and inside the bong. Makes it look brand new!!
Even easier? Oxiclean. Plug up the downstem, throw a couple scoops of Oxiclean in and fill with hot water. Walk away for an hour or two, come back and rinse. Sparkling bong, and absolutely no work.
also 1. fill with isopropyl alcohol and let sit for 10 mins 2. add rock salt, sea salt or anything that would not fully dilute and would be abrasive against resin 3. plug stem and cap mouth piece with hand 4. shake vigorously 5. rinse 6. repeat if necessary it is a little more work but it will clean it, and before anyone chimes in about the alcohol making your glass cloudy, it is simply not true. Been doing it for years on the same pieces and they are crystal clear.
I do the method mixted described but I've heard the salt can scratch glass but I also heard a lot of other things in my years as a human.
I just use a carboy brush and iso+salt...gets my bong looking brand new...now I only have straight tube germ. roor with no percs...just glass ...I also clean my tubes every week after use, and in between use I will replace my carbon in my carbon filter...keeps the water clean..when it turns yellow I replace...but the bongs themselves are spotless when I'm done cleaning. I think I might make a thread on how I clean my tubes, I know there are a few stickies which are helpful, but my routine has always worked awesome.
Remember this from high school " Mohs Scale" science pretty much trumps rumors every time. glass falls in at about 5.5 salt is about 2-3 salt simply will not scratch glass.