How to Remove Stains From a Fiberglass Sink

While brainstorming our laundry room makeover early in April, I looked at the sink, and I didn’t have much hope for it. Since replacing the fiberglass utility sink was out of the question and budget, I had to figure out how to remove all the stains or refinish it, so it could go back to being the clean white sink it once was.

This white fiberglass utility sink in the laundry room has been my basin where I clean and wash out all the paint and stain from my DIY projects. I would clean up after myself in a perfect world, but honestly, I was so done with our old laundry room that I let it go. The poor sink paid the price, and I had to find a way to remove all the paint and stains stuck to the fiberglass tub.

How to Remove Paint and Other Stains from the Sink

Before I begin, let me clarify that you do not need to remove the sink to clean it. That would be a bigger project! We removed the sink because we remodeled our laundry room last month.

If anything, it’s much easier to clean and remove stains from your sink while it is still hooked up to the water supply! I took the fiberglass basin to the patio and used a hose to clean it.

Here’s how the white sink tub looked like after several paint projects, including the most recent one, the painted laundry room cabinets in Denim blue.

remove stains from sink

Although oil-based paints (blue stain) are easy to clean up with soap and water, and elbow grease; wood stains (brown) are much more difficult to remove.

You can also notice the hard-water stains and calcium buildup on the top of the sink, where the faucet was. Even though I carefully chose a replacement faucet that would fit exactly like the old one we removed, I put a lot of effort into cleaning and removing the stains in that area of the sink, too.

This post contains affiliate links for your convenience. For more information, please read my Affiliates Disclosure.

Supplies Needed to Remove Stains from The Sink

There are several natural and chemical-free ways to remove stains from sinks. However, our fiberglass sink needed more than your usual peroxide, vinegar, or baking soda. While I have used these ingredients to clean and whiten stains from porcelain and stainless steel sinks, they were not powerful enough to remove all the stains in our fiberglass utility tub this time around.

how to clean fiberglass utility sink

Cleaning Tools and Supplies Needed

Note: I wasn’t planning to publish a tutorial on removing stains and cleaning an old fiberglass sink. I took these pictures for my Instagram Stories. Therefore, there’s only one picture showing you the actual cleaning process. Thanks for your understanding. 


Do Not Mix Cleaning Supplies

For safety reasons, I do not recommend mixing Mineral Spirits and Borax. Use them separately as I did. Once I removed all the stain and loosened up the paint splatters in the tub, I rinsed off the Mineral Spirits and then scrubbed using Borax.

1. Soak Stains

To remove paint and varnish stains from the sink, I used Mineral Spirits.

Mineral Spirits is a paint thinner, which is odorless but harmful. Please use with caution and in an open or well-ventilated area.

  • Pour a small amount of Mineral Spirits directly over the stains and let the product sit for 2 to 3 minutes.
  • With a circular motion, scrub the paint and stains using the scrubbing pad.
  • When you see that most of the stains and paint have loosened up, open the faucet and rinse the sink basin.
  • If the paint stains are too stubborn and you can’t remove them from the sink, repeat the process if necessary.

At this point, your sink should start looking cleaner. However, Mineral Spirits is an oil. Hence there are no coarse particles (as in borax or baking soda) that can scrub deep into the fiberglass of the sink. That’s when I decided to move to step 2.

2. Add Borax

I would say that the Mineral Spirits removed around 60% of the stains. Still, to clean stains (especially the brown varnish stain) deeply embedded in the fiberglass utility sink, I resorted to the use of Borax – one of my favorite natural cleaning products.

how to remove stains from sink
  • Rinse off the Mineral Spirits and any debris left in the sink.
  • Wipe the sink down using a paper towel or cleaning cloth. Do this to assess the sink and have a good idea of what stains are still left to remove and where.
  • Open the water supply and get the sink wet again.
  • Pour Borax over the stains and areas of the sink where cleaning is most needed.

The Borax will turn into a paste when in contact with water. It will clump, and then you can start scrubbing.

3. Scrub with Steel Wool Pad

Finally, take a steel wool pad and scrub the sink, putting more effort in the areas with stubborn stains.

Borax is a natural cleaning agent used to formulate laundry detergents. So do not fear to mix it with the soap in the steel wool pad. They’re both harmless. Remember, these are used to clean kitchens and surfaces that come in contact with food.

how to remove stains from sink

Watch all the stains disappear in front of your eyes! Using the Brillo pad worked like a charm, and even the most stubborn stain – like the calcium build-up in the faucet are- came off easily!

Notice that I did not scrub the sink’s drain because we changed both fixtures, the faucet and the drain. There is only one little speckle of gold paint that did not come off. But I am so happy with the result, and we saved ourselves some money in the laundry renovation project.

how to clean fiberglass tub

Have you tried removing stubborn stains from your sink? Let me know in the comments below!

Happy cleaning,