Tested: How to Get Tar Out of Knife Block Easily

By James Kowalski · December 23, 2025

Immediate Action (first 5 minutes)

You were cutting roofing felt for a shed repair, or maybe you were patching a bicycle tire with heavy-duty adhesive. You got distracted, wiped your Wüsthof chef's knife on a rag, and shoved it back into the bamboo block. Now there is a thick, black smear of petroleum tar deep inside the slot. Stop right there. Don't push the knife back in to test the fit.

In my experience cleaning kitchen gear for over 10 years, the biggest mistake people make is trying to wipe wet tar with a damp paper towel. Water and petroleum don't mix. You'll just drive the sticky residue deeper into the porous wood fibers. Grab a flashlight. Shine it down the slot. You need to see exactly where the black smudge starts and ends before you blindly start poking around.

Pull the contaminated knife out immediately. Wipe the blade clean with a dry paper towel and a drop of dish soap. Set it aside. Your primary goal in these first 5 minutes is containment. If the tar is still wet and tacky, it hasn't fully bonded to the wood's finish yet. This gives you a massive advantage. I'll be honest, this takes elbow grease later if you let it cure, so act fast. Keep the block upright and avoid tilting it, which could cause the tar to drip down into the bottom reservoir of the block where it's nearly impossible to reach.

What You'll Need (tools/products)

Tar is a stubborn, petroleum-based hydrocarbon. You can't just use standard all-purpose cleaners like Method or Mrs. Meyer's. You need a solvent that breaks down carbon chains without dissolving the glue holding your knife block together. I've tested dozens of degreasers, and these are the exact tools and products I keep in my cleaning caddy for this specific nightmare.

The Solvents

Klean-Strip Odorless Mineral Spirits ($12-15 per quart): This is my top choice for raw or lightly sealed beechwood blocks. It cuts through tar in seconds but evaporates slowly enough to let you work.
Goo Gone Original Citrus Gel ($6-8 for 8oz): Best for bamboo blocks. The gel formula clings to the vertical walls of the knife slot instead of dripping straight to the bottom. The d-Limonene naturally breaks down the tar.
Dawn Platinum Powerwash Dish Spray ($5): You'll need this for the final degreasing step to remove the oily solvent residue.

The Tools

Bamboo Skewers (3/4 inch thick): Don't use metal tools. A butter knife or screwdriver will permanently gouge the soft interior walls of the block.
Q-tips Cotton Swabs: Buy the ones with paper sticks, not plastic. Plastic sticks snap when you apply lateral pressure inside a tight 1-inch slot.
Nitrile Gloves: Tar stains skin for days, and mineral spirits will dry out your hands terribly.
LED Penlight: A 200-lumen pocket flashlight is crucial for inspecting the bottom corners of the slot.

Solvent Type	Best For Block Material	Dwell Time	Odor Level
Mineral Spirits	Beechwood / Walnut	2-3 minutes	Low (if odorless)
Citrus Gel (Goo Gone)	Bamboo / Acacia	5-7 minutes	High (Sweet Orange)
WD-40 Specialist Citrus	Plastic / Acrylic	1-2 minutes	Medium

Step-by-Step Removal

This isn't the fastest cleaning job you'll ever do, but it is the safest for your expensive knife block. If you rush and scrub too hard, you'll strip the finish and leave the wood vulnerable to mold. Follow these exact steps.

Step 1: Dry Mechanical Scraping

Take a dry bamboo skewer and gently scrape the surface of the tar smudge. Hold the skewer at a 45-degree angle. You want to lift the bulk of the physical mass off the wood without pressing it into the grain. If the tar is thick, you might get a few satisfying chunks to peel away. Discard the skewer once the tip is coated. Don't reuse it, or you'll just smear the black gunk around.

Step 2: Apply the Solvent Gel

Squeeze a pea-sized amount of Goo Gone Citrus Gel directly onto a cotton swab. Jam the swab into the slot and press it firmly against the tar stain. Hold it there for exactly 4 minutes. The d-Limonene needs time to penetrate the petroleum bonds. If you're using mineral spirits on a beechwood block, soak the cotton swab until it's dripping, but work quickly so it doesn't pool at the bottom.

Step 3: Agitate and Lift

After the dwell time, use a fresh, dry cotton swab to scrub the area in tight circular motions. You'll see the black tar instantly turn into a brown, muddy sludge. This is the chemical reaction working. Wipe the sludge away with a dry paper towel. Repeat this apply-and-lift process until the cotton swab comes out completely clean. I usually go through 6 to 8 swabs per slot.

Step 4: The Dawn Degrease

Solvents leave behind an oily film that will attract dust and ruin your knife handles. Mix 1 tablespoon of Dawn Platinum Powerwash with 1 cup of warm water (around 90°F). Dip a microfiber cloth into the solution, wring it out until it's barely damp, and wipe down the interior of the slot. The Dawn will emulsify the remaining solvent oils. Follow up with a dry cloth.

Step 5: Inspect and Dry

Shine your LED penlight down the slot. Look for any dark shadows or sticky spots. If it's clean, leave the block in a well-ventilated room with a fan pointing at it for 24 hours. The wood needs to completely off-gas and dry out before you put your knives back in. Moisture trapped in a dark slot is a recipe for black mold.

Step 6: Recondition the Wood

The solvent stripped the natural oils from the wood. Once the block is 100% dry, apply a generous coat of food-grade mineral oil to the interior and exterior. Let it soak in for 2 hours, then buff it with a clean rag. Your block will look better than the day you bought it.

Alternative Methods

Sometimes you don't have Goo Gone or mineral spirits on hand, or you're dealing with a non-wood block. Here are three backup methods I've used when the standard approach isn't an option.

The Freezer Trick (For Plastic/Acrylic Blocks)

If you have a modern acrylic block like the Kapozi or Messermeister clear models, solvents can sometimes cloud the plastic. Instead, put the entire empty knife block in your kitchen freezer for 3 hours. The extreme cold (usually 0°F) causes the tar to become brittle and shrink. Take it out, insert a butter knife into the slot, and the frozen tar will pop off in one solid piece like a scab. It's incredibly satisfying and uses zero chemicals.

The Peanut Butter Method (Food-Safe Only)

If you are deeply paranoid about using petroleum solvents near your food prep tools, use creamy peanut butter. The natural oils in the peanuts act as a mild, non-toxic solvent. Smear a thick layer of Jif or Skippy onto the tar, let it sit for 12 hours, and scrape it away. I'll be honest, this takes way longer and requires a lot of dish soap to clean up the grease afterward, but it is 100% food-safe.

WD-40 Specialist Citrus Cleaner

Standard WD-40 leaves a terrible, lingering mechanical smell that will transfer to your bread knife. However, the WD-40 Specialist Citrus Cleaner (the green can) is formulated to evaporate cleanly. Spray it onto a rag, wrap the rag around your bamboo skewer, and run it up and down the slot. It works in about 60 seconds flat. This isn't the cheapest option, but it's a lifesaver if you're in a rush.

Prevention Tips

Getting tar out of a knife block is a chore you only want to do once. After hosting a dinner party where I had to explain why the kitchen smelled like a gas station, I completely changed how I handle messy DIY projects.

Buy a Dedicated Utility Knife: Keep a $10 Stanley FatMax folding knife in your garage or junk drawer. Never use your kitchen cutlery for cutting shingles, tar paper, or bicycle patches. The carbon steel in kitchen knives reacts weirdly with roofing adhesives anyway.
Use Blade Guards: If you absolutely must bring a messy tool into the kitchen, slide a plastic blade guard over the knife before storing it. A $15 pack of universal edge guards from NobleHome & Chef will protect the interior of your block from any rogue adhesives.
Switch to a Magnetic Strip: I eventually threw away my bulky bamboo block and installed a 16-inch Ouddy magnetic knife strip on the backsplash. It holds my Zwilling set perfectly, takes up zero counter space, and makes cleaning up accidental tar smudges as easy as wiping a flat surface with a rag.

FAQ

Will mineral spirits ruin the wood finish of my knife block?

Yes, mineral spirits will strip the natural oils and factory finish right off the wood. However, this is actually a good thing because it allows you to re-oil the block with food-safe mineral oil afterward. You'll end up with a block that looks brand new and is properly sealed against future moisture.

Can I just put the whole knife block in the dishwasher to melt the tar?

Absolutely not, as the extreme heat and harsh detergents will warp the wood and crack the glue joints. Dishwashers operate at around 140°F to 160°F, which is hot enough to damage the structural integrity of a bamboo or beechwood block. Stick to manual spot-cleaning to preserve your investment.

How do I get the strong solvent smell out of the wood afterward?

I recommend placing the empty block in a well-ventilated area with a small bowl of dry coffee grounds or baking soda sitting nearby. The porous wood will off-gas the petroleum distillates over 24 to 48 hours, while the coffee grounds absorb the ambient odors. If it still smells after two days, wipe the interior slots with a damp cloth and white vinegar.

What if the tar is hardened and rock solid inside the slot?

Hardened tar requires a longer dwell time with your solvent to break down the petroleum bonds. Soak a cotton ball in Goo Gone, jam it into the slot with a skewer, and let it sit for exactly 15 minutes before scraping. The chemical reaction will soften the tar back into a manageable, sticky paste.