I'm going to go through two examples, one for a spoon or hand-bubbler, and one for a bong.
If you like, I highly recommend picking up a pack of assorted fish tank cleaning brushes at the aquarium supply section of your favorite box store- it's like $3 and worth every penny.

Let's start with your cleaning solution. There are several commercial cleaners on the market, but they can be pricey and I don't feel that they are good enough to warrant the high cost. These solutions have two basic components: A solvent, and an abrasive.

Solvent:
Cannabis resins and the tars resulting from their combustion are soluble in a non-polar solvent, or one that ACTS non-polar. In your house, you probably have a few of these laying around- paint thinner, kerosene, rubbing alcohol, even that dusty bottle of Bacardi 151 you haven't touched since discovering pot, lol... However, not all of these solvents are appropriate for this task, as they leave nasty residues. True alcohols have the GREAT property of being 'miscible' with water, which is a polar substance. So even though the tar doesn't DISSOLVE in the water itself, it dissolves in the carrier solvent, which then mixes with water and can be completely washed away. This is actually the concept behind an isopropanol hash extraction but that's another story for another day.
So the solvent you want to use is Isopropanol rubbing alcohol, at the highest concentration you can buy. I believe you can get 90% iso at pharmacies. The second choice would be high-proof booze but that's REALLY inefficient, expensive, and less effective.
Other, higher molecular-weight hydrocarbons such as fuels and paint thinners are very dangerous and should NEVER be used.

Abrasive:
What do you want that will gently rub away caked-on tars and other residues, but not damage the glass?
SALT!
Salt is great. Table salt works passably, but if you can get something chunkier such as Kosher or Rock salt, that's even better.
Why does salt work as an abrasive? It's because it is only significantly soluble in a polar solvent (=water), and in a nonpolar solvent, retains its solid form and sharp edges. But there's water in your rubbing alcohol? No problem, you are going to use EXCESS salt, so that the water is saturated, and no more can dissolve.

Let's try your spoon bowl or a slider first, because these items are small.

Take a 'snack' or 'sandwich' sized ziploc baggie that is large enough to hold your piece. Don't skimp on the quality- the heavy duty name-brand bags are less likely to fail and leak dirty resin-slop all over you as reward for your efforts! Now put in a couple hefty scoops of salt, trying to get a bunch of it INSIDE the pipe, and then pour in enough rubbing alcohol to submerge it. Seal the ziplock, and put the whole thing in a larger ziploc, and seal that.

Now shake it. HARD. You'll soon see little black flecks in the liquid- that's your buildup. Keep shaking until you think the piece is clean. Add more salt and alcohol if you need to.

Now take it out, swish it briefly in the alcohol, and rinse it out under really hot tap water. Inspect and repeat if necessary. If there's a stubborn spot, take one of your aquarium brushes and dampen it with alcohol, then dip it in more salt and scrub away! You can use the 'dirty' alcohol/salt mixture for the second cleaning if you see there's enough solid salt in there.

Your bong is a little harder, but not quite. It helps to have a pair of corks for it- one to fit the opening to the downstem, and the other for the mouth opening. You can get corks at most crafts stores, or save them from other liquids. Champagne corks have a fat head that will, under pressure, block the opening to most bongs. The downstem opening may need you to cut a cork down to a smaller size.

Take your alcohol and salt mixture and pour it into the bong. If the top cork is not tight on its own, you'll have to grip it in place. Make sure you have plenty of salt and shake that thing until it's clean! Again, you might have to go in with an aquarium brush to get bits of crud, especially in the angle between the downstem and body of the piece. Rinse under hot water and you're good to go!
stinkyattic Reviewed by stinkyattic on . Care and cleaning of your glass pieces Hello all, I just wanted to post up a thread discussing pipe maintenance. There used to be a resin cleaning guide, but I and others feel that smoking resin really isn't a legit medical method- Old resin inside your pipe is not really something desirable to smoke, even though, yes, it does serve in a pinch. I'm more interested in methods of getting resin buildup out of your pipe so that your smoking experience is as pleasant and healthy as possible. A clean bong is a happy bong! Rating: 5