I recently spent a week or so trying to unclog a seriously blocked kitchen sink drain. I tried various things, including One Shot Instant Drain Cleaner (a hardware-store 91% sulphuric acid drain cleaner).

My attempts all failed and eventually a plumber managed to solve the problem in about five minutes' flat with a glorified Henry Hoover...

Alas, I hadn't noticed at the time that I'd spilled a small amount of the cleaner on my sideboard. It's now dried into a thin layer of a cement-like material. Scraping it off with a screwdriver seems like it might eventually be successful, though after quite some time and I'm concerned about damaging the sideboard.

Is there a compound that I can use to just dissolve the dried drain cleaner, or at least convert it into some form that I can then clean up? Boiling water on its own doesn't seem to do anything at all.

Click for full size:

image of the dried cleaner


1 Answer 1


Put on good rubber gloves, preferably ones that are made for handling hazardous chemicals, and safety goggles.
Make a thick paste with a cup of baking soda and cold water and spread it over the area to neutralize the sulfuric acid. Even though it has dried it is still active. Let the paste sit for 10-15 minutes before touching it. You may want to open a nearby window as this can release a fair amount of CO2.

Using a 2 inch or larger putty knife, carefully scrape away part of the baking soda to reveal the counter. Next carefully scrape at the edges of the spill. Keep doing this until all of the baking soda is gone.

I can't tell from the picture if your counter top is a type of laminate or granite. If it is laminate you may find that the "cement-like material" is actually your counter top and the acid has melted it. If it is granite you may need to have the counter professionally polished to get rid of the stain.

Best of luck

  • Yeah, I think it was the laminate itself. I never did resolve this. I've had a granite "worktop saver" covering that area ever since. Commented Feb 3, 2013 at 16:36
  • For the record, when I moved out last September, I just took a hit on the damage deposit. No idea how they resolved this, if they did. Commented Apr 5, 2014 at 17:44

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