What Are Cannabis Glass Filters? Tips and Screens Explained

Short answer

A cannabis glass filter is a small borosilicate glass part placed between the burning flower and your mouth. The name covers two items. A glass filter tip is a mouthpiece for a joint, blunt, or pre-roll. A glass screen is a disc that sits in the bowl of a pipe or bong to keep ash and flower from pulling through.

Cannabis Filter Tips: Types, Sizes, and How to Use Them

Glass filter tips

Tips are hollow tubes. Common diameters are 6 mm, 7 mm, 8 mm, 10 mm, and 12 mm. Lengths run 20 mm to 45 mm. Most have a raised ridge near the outer end. The rolling paper tucks under that ridge, so the tip stays in the roll.

best filter tips for joints and blunts

Borosilicate glass has a low rate of thermal expansion, about 3.3 x 10^-6 per degree C. It softens near 820 C. The burning end of a joint reaches 600 C to 900 C, but the tip sits 30 mm to 70 mm behind the cherry, so it stays cool enough to hold.

how to fit a filter tip in a joint

How to roll with a glass tip

1. Hold the tip with the ridge at the mouth end.
2. Wrap the paper around the tube. Keep the tube hole clear.
3. Fill with ground flower. Pack it firm near the tip so it does not shift.
4. Twist the open end, light, and draw.

Glass screens

Screens are flat discs, 8 mm to 20 mm across. Three shapes show up in shops:

How to Fit a Filter Tip in a Joint: A Comprehensive Guide

• Daisy screen: holes punched in a flat disc.
• Jack screen: a disc with three or four bent legs that hold it off the bowl floor.
• Honeycomb screen: a grid pattern with more open area.

They drop into the bowl before the flower. Ash falls through the holes. Flower does not.

What a glass filter does

• Cools smoke. Glass pulls heat off the air path.
• Stops flower and ash from reaching your mouth.
• Holds the shape of a joint at the mouth end.
• Replaces paper crutches, which get soggy and burn.
• Replaces brass and steel screens, which can add a metal taste.

What a glass filter does not do

Glass tips and glass screens do not filter tar, resin, or cannabinoids. They are mouthpieces and barriers, not filters in the cigarette sense. Smoke still carries tar, carbon monoxide, and fine particulates. A water pipe percolator is not a filter either. It cools and spreads smoke, and water catches some tar.

Cleaning and reuse

1. Drop the glass in a jar of 91% isopropyl alcohol. Wait 30 minutes.
2. Shake the jar. Use a pipe cleaner on tube interiors.
3. Rinse with warm water. Let it dry.

Skip boiling water and skip the dishwasher. Thermal shock cracks borosilicate. A tip or screen lasts months to years with regular cleaning.

Cost

Glass tips sell for $2 to $15 each. Glass screens sell for $1 to $6 per pack. Colored glass costs more than clear glass. Color does not change function.

Labels vary

Some shops list a bong downstem or an ash catcher as a glass filter. Check the photo. A downstem moves smoke from the bowl to the water. An ash catcher traps ash before the main chamber. Neither part filters tar from the smoke you inhale.