How to Clean a Weed Grinder (Kief First, Then by Material)

To clean a grinder, harvest the kief first, then take the grinder apart, soak the metal pieces in 91 to 99 percent isopropyl alcohol for 20 to 30 minutes, scrub the teeth, threads and screen with a toothbrush, rinse in warm water, and let everything dry completely before you reassemble it. That works for anodized aluminum and stainless steel, which covers most weed grinders. Acrylic, wood, coated and electric grinders need gentler methods, and you can skip the alcohol entirely if you have to.

We haven't soak-tested every material, so the advice for each comes from the makers' own care pages where they publish them (several don't), plus our time with the Chewy G3 for our electric grinder guide. The vaporizer itself is covered in our guide to cleaning a dry herb vaporizer.

Contents9 sections

1. What You Need
2. Step 1: Harvest the Kief Before You Clean
3. Step 2: Take It Apart
4. Step 3: Clean It by Material
5. How to Clean a Grinder Without Alcohol
6. How to Fix Sticky or Stiff Threads
7. How Often Should You Clean a Grinder?
8. When to Replace a Grinder
9. Frequently Asked Questions

What You Need

• Isopropyl alcohol at 91 to 99 percent (70 percent is nearly a third water and slower on resin)
• A jar or zip bag big enough to cover the pieces
• A stiff toothbrush, plus pipe cleaners or cotton swabs for the holes
• A plastic pick; SLX suggests a guitar pick 0.50 to 0.70 mm thick, because metal gouges finishes
• Dish soap, warm water, a towel and a sheet of paper

Step 1: Harvest the Kief Before You Clean

Kief that goes into an alcohol bath is gone, so collect it first.

1. Freeze it. Put the assembled grinder in a zip bag in the freezer for 20 to 30 minutes. Cold makes trichome heads brittle and stiffens the resin, so both let go of the teeth and screen more readily, the same reason ice water hash is made with ice.
2. Tap it out. Hold it over a sheet of paper and tap it firmly on a hard surface, lid side up, so loose kief drops through the screen.
3. Scrape the catcher. Gather the kief with the scraper, then brush the underside of the screen gently with a soft, dry brush.
4. Clear the teeth while they're cold. Chilled resin chips off with a plastic pick or a stiff dry brush instead of smearing.

Go easy on the screen. Space Case's warranty excludes screens damaged by a carelessly stored pollen pick, and tells owners to check the pick lies flat before the grinder goes back together. What to do with the harvest is in our guide on what to do with kief.

Tip: If you're only harvesting kief, let the grinder warm up and wipe off the condensation before it goes back into service. Damp flower is where mold starts.

Step 2: Take It Apart

• Screens: Most are pressed in for good (Space Case uses a tapered locking press), so leave them. Kannastör's Easy Change Screen is designed to come out, so clean both sides.
• O-rings and friction rings: Space Case grinders turn on nylon O-rings, and Kannastör's GR8TR V2 uses friction rings. Pull any ring that comes out easily and wash it separately in soapy water.
• Stickers and logos: Santa Cruz Shredder warns that liquids ruin its sticker adhesive, and SLX says harsh solvents can discolor its logo. Keep labels out of the soak.

Step 3: Clean It by Material

Anodized Aluminum and Stainless Steel: The Isopropyl Soak

1. Soak. Cover the pieces with isopropyl in a jar or zip bag. Twenty to 30 minutes handles a routine clean; a neglected grinder can sit for an hour or two. Shake it now and then.
2. Scrub. Work a toothbrush over the teeth, threads and holes, and push a pipe cleaner through any hole still blocked. Brush the screen lightly from both sides; never poke it.
3. Rinse warm, not boiling. Rinse with warm water and a drop of dish soap, then clear water, until the alcohol smell is gone. Magnetic lids use rare earth magnets, usually neodymium, and K&J Magnetics rates standard N-grade neodymium to 80°C (176°F), above which some strength can be lost for good. Makers don't publish the grade, and boiling water is 100°C.
4. Dry completely. Towel the outside and leave the pieces apart for a few hours, overnight if you can. Water hides in the threads and under the screen.

Warning: Isopropyl is a flammable liquid with a flash point of 53°F (12°C), according to the NIOSH Pocket Guide, and its vapor irritates eyes, nose and throat. Soak in a ventilated room, away from stoves, candles and the torch you use for a DynaVap. Pour the dirty alcohol away afterward; never dry it down to vape or smoke the resin it pulled off.

Zinc Alloy Grinders

Budget grinders that feel heavy for their size are usually zinc alloy with a painted or plated finish, and paint lifts in a long soak. Soak for the minimum and inspect the teeth afterward. If the finish is flaking into the teeth chamber, replace the grinder, because those flakes end up in your oven.

Acrylic and Plastic Grinders

Alcohol is the wrong solvent here. The maker of ACRYLITE acrylic sheet lists alcohol among the solvents that cause crazing, a web of fine surface cracks, and approves isopropyl only diluted to 30 percent (ACRYLITE care guide). Storz & Bickel agrees about its acrylic Herb Mill, the one in the Volcano box (see our Volcano accessories guide): its Mighty+ instructions say the mill washes in warm water only, because alcohol damages its surface. Soak plastic pieces in lukewarm soapy water for 30 minutes, scrub, rinse and dry.

The exception is Santa Cruz Shredder's hemp range, which Santa Cruz says is completely safe to clean with isopropyl as long as liquid stays off the sticker. For any other plastic, find the maker's word before using alcohol.

Wood Grinders

Never soak a wooden grinder. Wood swells when wet, which is how wooden grinders warp and loosen their pins; RYOT promises its walnut 1905 grinders won't warp or lose pins, which tells you the usual failure. Freeze it, brush the teeth with a dry toothbrush, clean the steel teeth with a swab dampened with isopropyl, and wipe the wood with a barely damp cloth.

Ceramic and Non-Stick Coated Grinders

SLX, which says it pioneered ceramic-coated grinders, says on its care page that its grinders generally won't need cleaning, with buildup mostly appearing when flower is above 12 percent moisture. It asks owners to tap the grinder out over paper after every use and brush the teeth occasionally. Rubbing alcohol and acetone are safe on the coating, though they can discolor the logo. Never scrape a coated grinder with metal, which can chip the coating; use a plastic pick, and for stubborn buildup SLX recommends refined hemp seed oil to loosen it.

Electric Grinders

Never put an electric grinder in water. The Chewy G3 manual lays out the routine:

1. Slide the built-in screwdriver between the blades and pull the blade ring upward.
2. Clean the blade with a cotton bud and a little cleaning alcohol or coconut oil.
3. Pull back the trigger and swab the chamber and the push block the same way.
4. Brush out loose material with the included brush.
5. For a deep clean, remove the two screws beside the door hinge to take out the trigger and push block.

Chewy warns that skipping cleaning may void the G3's 12 month warranty. In our testing it stayed fairly clean as long as the flower was dry enough. For a blade coffee grinder used on flower, unplug it, brush it out, wipe the blades with alcohol on a paper towel, and keep the motor base dry. How these compare with a manual grinder is in our guide on how to use a weed grinder.

How to Clean a Grinder Without Alcohol

1. Freeze and brush. Chill it for 30 minutes or more, then brush the teeth and threads hard with a dry toothbrush. On a lightly used grinder this is all you need.
2. Soak in warm soapy water. Thirty to 60 minutes in hot tap water with plenty of dish soap softens resin enough to scrub off, though it won't match alcohol on a neglected grinder.
3. Use a food oil. Chewy lists coconut oil as an alternative to alcohol on its blades, and SLX recommends refined hemp seed oil for buildup. Rub a little onto the teeth, wait a few minutes, scrub, then wash the oil off with soap.

How to Fix Sticky or Stiff Threads

A grinder that won't close or turns like it's full of sand has resin and plant dust in the threads or on its ring.

• Clean the threads: Run a toothbrush dipped in isopropyl around every thread (soapy water for plastic), then rinse and dry.
• Replace a worn ring: If the O-ring is flattened or split, replace it. Space Case sells replacement nylon O-rings for $3 to $4.
• Start the thread properly: Turn the piece backward until you feel it drop into the thread, then forward. Cross-threading is how aluminum grinders get ruined.
• Lubricate sparingly: SLX recommends a drop of refined hemp seed oil when its grinders turn stiffly.

How Often Should You Clean a Grinder?

• Every use: Tap it out over a tray before you put it away, as SLX recommends.
• When the catcher has a visible layer: Harvest the kief using Step 1.
• When it shows the signs: Turning gets stiff, herb clumps in the teeth, the screen stops passing kief, or the last strain's smell hangs on. For a daily user, once a month is a reasonable reminder, but the signs are the better guide.

A clogged grinder tears instead of cutting, and an uneven grind heats unevenly (our grind and packing guides explain why). If yours gums up every few days, the flower is probably too moist; see our humidity guide and the best way to store weed.

When to Replace a Grinder

Warranties differ more than the marketing suggests. Santa Cruz Shredder's lifetime warranty covers only teeth broken in normal use, on grinders bought from an authorized dealer. Kannastör's covers manufacturer defects including broken teeth for any reason (RYOT), and its screens get 30 days. Space Case's excludes scratches, dents, improper care, worn O-rings, pollen picks and anything bought on Amazon or eBay. When it's time for a new one, our accessories page has grinders alongside the rest of the kit.

Frequently Asked Questions

How do you get all the resin out of a grinder?

Freeze it and chip off what you can with a plastic pick, then soak the metal pieces in 91 to 99 percent isopropyl for an hour or two and scrub the teeth, threads and holes with a toothbrush. A badly neglected grinder may need a second soak.

Can I clean a grinder without using alcohol?

Yes. Freeze it and brush it dry, soak it in hot soapy water for 30 to 60 minutes, or work a little coconut or refined hemp seed oil into the resin and wash it off with soap. It is slower on heavy buildup, and it is the right method for acrylic grinders anyway.

Can I freeze my grinder to clean it?

Freezing helps but doesn't finish the job. Twenty to 30 minutes in the freezer makes kief and resin brittle, so the kief taps loose and resin chips off, but nothing dissolves. Freeze, harvest, then wash.

Can you put a grinder in the dishwasher?

Not a metal one. None of the makers we checked list their aluminum grinders as dishwasher safe, and alkaline dishwasher detergent attacks anodized finishes. Wash it by hand.

Can you smoke or vape the resin from a grinder?

Not resin that has been in an alcohol bath. It carries the solvent and whatever came off the grinder, so throw it out. Dry kief collected before any liquid touches the grinder is a different thing, and our kief guide covers it.

How long should a grinder soak in isopropyl?

Twenty to 30 minutes for a grinder you clean regularly, an hour or two for a sticky one. Keep acrylic, wood, painted grinders, O-rings and anything with a sticker out of the soak.