How to Get Rid Of Black Dots on Window Sill

The black dots on your window sill are dangerous. They represent a black mold that could multiply and move to hard-to-clean areas of your home. These spots could be anywhere from the tiny cracks in your walls to the openings within your HVAC system.

Such growth of mold can lead to serious health problems. People living in homes with high amounts of mold spores are at greater risk of developing fungal infections, asthma episodes, sinus congestion, and irritations of the eye, nose and throat.

The good news is that the issues highlighted thus far aren’t unstoppable. You can stop them in their tracks if you know how to get rid of black dots on window sill. This approach would also save you from looking for replacement windows anytime soon.

How to get rid of black dots on window sill

Follow these instructions to remove black dots from the window sill:

What you’ll need?

  • Gloves, goggles and dust mask
  • 1 sheet of plastic cover
  • Hand vacuum with built-in HEPA filter
  • Bleach and warm water
  • Stiff nylon brush
  • Old rags or worn-out newspapers
  • Dry clean rag
  • Sandpaper
  • Vinegar

Step-by-Step Guide

  • Step 1: Put on your safety gear

Don the gloves, safety goggles and dust mask. As WCMA Window & Door said, Mold spores can be dangerous if inhaled, especially for individuals with allergies, compromised immune systems and respiratory problems. It’s recommended that you shouldn’t take any chance with your safety.

  • Step 2: Inspect the window

Inspect the entire window from inside and outside. Try to identify mold under hardware, on sashes and in window seals. Make sure that you don’t miss a spot with visible mold growth. Or else you may have to do the job over again in a few months’ time.

  • Step 3: Cover the furniture and floor

Cover everything close to the window with a sheet of plastic cover. This will make sure that the mold spores and dirt particles from the window won’t end up making their way into the flooring or carpet. It is also recommended that you turn off the HVAC system at this point.

  • Step 4: Open the window

Opening the window is crucial as you’ve to access its casing and the entire sill. That is why we recommend that you do this project on a cool, breezy day. Postpone the work to another day if the weather is too hold or cold for your liking.

  • Step 5: Vacuum the sill

Use a dry vacuum with built-in HEPA filter for this purpose. The dry cleaning session will pick up dirt particles and spores, making it easier for you to scrub surfaces later on.

  • Step 6: Scrub the entire window

Prepare a mixture of warm water and bleach and use it to scrub the window from top to bottom. Use a stiff nylon brush to remove stubborn black dots and a couple of old rags to remove excess water as you scrub away the mold spores.

  • Step 7: Dry the window

Use a clean, dry cloth to wipe down the window. Afterward, let the window remain open until you’re sure it is fully dry. This step is crucial as if you close the window while it’s still wet, the remaining moisture can contribute to mold growth.

  • Step 8: Sand away stubborn stains

Stubborn black dots might not go away with a mere scrubbing session. You may have to sand them away with a finer-grit sandpaper.

  • Step 9: Vacuum the window

Once again vacuum the entire window, including its panes, inside jambs and tracks and both the upper and lower sashes. This will help clear any remaining dirt particles. Follow this up by folding the plastic sheet and throwing it in the dust-bin.

After you remove black dots from window sill

Here’s what you need to know:

How do black dots get on window sill?

The blowing of wind can deposit mold spores on your window sills, casings and frames. Once they are deposited on the surface, the heat from the sun and the moisture from frame condensation can allow the black dots to multiply very quickly.

Potted plants can also contribute to the presence of black dots on window sills. They have built-in mold spores which they can transfer to the sill without a notice. Plants also add to the humidity of the place when they excrete water, thereby creating a perfect breeding spot for black dots.

Condensation also contributes to the build-up of black dots on window sills. It sets in when the window has a crack that lets in rain water from outside, or when the ventilation in the bathroom is poor and allows the moisture to condense on the window from the inside.

Lastly, if you cover your window with heavy drapes during the winter, the resulting shade allows moisture to fester beneath the curtain. That in turn allows black mold to thrive as it blooms in areas that are shaded from direct sunlight and have vast amounts of moisture.

How to prevent black dots from reappearing on window sill?

Follow these tips to prevent the reoccurrence of black dots on the window sill:

  • Make sure that there aren’t any cracks or leaks in the window.
  • Reduce the number of plants close to the window
  • Ensure proper ventilation in rooms with high humidity, i.e., washrooms
  • Frequently open windows to increase the flow of air through the room
  • Ensure that the weather stripping and window caulking are in good shape
  • Habitually draw back curtains to reduce the rate of frame condensation
  • Dry clean the window frequently to prevent the build-up of moisture
  • Set your home heater at 15*C during the winters to prevent condensation on windows
  • Dry wet materials quickly as mold only requires 48 hours to grow
  • Avoid the use of flue-less gas heaters as they produce water in the form of water vapors
  • Paint your home with anti-condensation and anti-mold paint (optional)


Black dots on window sills are an indicator of a far deeper problem. You shouldn’t ignore them as leaving them be can be dangerous for the health of your entire household. Also, once you have removed the dots using the abovementioned procedure, follow the tips we have given to prevent their reoccurrence.