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Zinsser Mold Killing Primer Review: Does It Work?

This is a review of Zinsser Mold Killing Primer, what it does, where you should use it, and how I use it.

I have been painting for roughly 20 years now. I’ve done everything from kitchen cabinet painting to exterior painting, and restoration work.

Zinsser Mold Killing Primer and Tools

I actually come into projects with mold issues quite often. The typical mold issues I run into are moldy bathroom ceilings & walls, mold on walls after removing wallpaper, moldy window sills, and moldy drywall in basements.

Zinsser Mold Killing Primer has become my go to choice for dealing with these mold issues since it is easy to use, redily available, and is from a brand I trust and use often (Zinsser Smart Prime, and Zinsser Peel Stop are two of my favorite primers).

Special Note About Mold

It is worth stating that I am not a mold remediation specialist, nor is Zinsser Mold Killing primer a professional encapsulation product. It is simply a primer that has agents added to help kill mold. I recommend hiring a mold specialist for large mold problems and only recommend this product for small mildew issues where the root cause has already been addressed.

Zinsser Mold Killing Primer Overview

Bathroom Primed with Zinsser Mold Killing Primer
Walls primed with Zinsser Mold Killing Primer. Wainscoting primed with Smart Prime & MKP.

Zinsser Mold Killing Primer is a water based primer that has an EPA registered antimicrobal added into the primer that will help in killing existing mold and mildew as well as preventing future mold and mildew growth.

Below, I am going to show you how I use Zinsser Mold Killing Primer, where you should use it, and how to properly apply it to get the best results possible. I’ll also go over some of the technical and safety info for those of you who want to read even more information.

Does Zinsser Mold Killing Primer Work? Should You Use It?

Lets start off with this basic question, does Zinsser Mold Killing Primer work?

In my experience yes, it absolutely works. I know this because if it didn’t work I would get callbacks on my work. I know a product worked and did it’s job well when my clients don’t call me back to fix old painting jobs.

I state in my contracts that I offer a 3 year warranty on my work, but in reality, if someone calls me 5+ years later, I have no problem coming and fixing an issue if it is related to me.

I’ve been using Zinsser Mold Killing primer as my primer of choice in every bathroom that has a shower or tub for nearly 10 years. During this time, I have not had any callbacks due to mold, bleed through, or adhesion issues in bathrooms.

I should say though, that this primer is not a solution to legit mold issues in my opinion. It is perfect for a preventative primer or to prime small mold/mildew issues that have already been addressed. This is just my opinion.

I would never paint a room unless the moisture issues have already been solved. For example, if a bathroom does not have a vent fan, you’ve got bigger issues that need to be addresses, or if a basement frequently floods, or a ceiling has a leak, these all need to be addressed prior to thinking you can fix the issue with a primer.

First, stop the moisture issue. Then do your best to clean the mold before priming. I won’t get into mold killing/cleaning methods. I’ve learned to stay away from those topics as the trolls will attack if I say anything!

Where You Should Use Zinsser Mold Killing Primer

Obvisouly use Zinsser Mold Killing Primer anywhere that you’ve already had any mold or mildew issues and have already addressed the source of the mold/mildew.

Using it as a preventative, I recommend priming your bathrooms with it, using it under sinks, priming basement drywall that has moisture potential, and anywhere else that may exposed to moisture / high humidity.

Personally, I have a large shop in my back yard that has had moisture issues around the bottom 2 feet and have had mold grow on my painted block.

I used Zinsser around the bottom two feet of my shop, painted a top coat over it, and have not had any issues since.

How To Apply Zinsser Mold Killing Primer

There is really no special application process for this primer. Zinsser does recommend not thinning before you apply though.

A simple brush and roll application should be good for most projects. If you need to prime a ceiling, I highly recommend renting or purchasing a sprayer to help you with the task as rolling ceilings can be very difficult and result in causing more damage to the ceiling.

VOC Levels and Safety

I didn’t used to pay any attention to the VOC level in the paints I used when I was younger. These days however, my health is of the highest importance.

Zinsser Mold Killing Primer has less than 100 grams per liter of VOCs. While this is a bit high for a water based product, it is still drastically lower than any oil or shellac primers.

For reference, Kilz Original (oil based) has over 400 grams per liters, while Zinsser Smart Prime (water based primer) has less than 40 grams per liter.

At a minimum, make sure to have good air flow when using this product. Ideally, use a 3M carbon cartridge respirator. Check out The Best Respirator For Every Painting Project for more info on respirators.

Dry Time

Zinsser Mold Killing Pimer is typically dry to the touch in 30 minutes and can be top coated within 1 hour. This will vary due to humidity. If you need to help speed up the drying process, check out my post on How To Make Paint Dry Faster.

Zinsser also recommends that you top coat over the mold killing primer within 72 hours of application. This primer is not made to be a top coat and must be coated over in order to last.

Alternatives to Zinsser Mold Killing Primer

There are many different primers on the market and each has a specific purpose. You would probably have decent luck with many all-purpose primers if you have already killed and cleaned your mold and mildew issue and the moisture problem is already solved.

Kilz Mold and Mildew

Zinsser Mold Killing Primer Review: Does It Work? 5Zinsser Mold Killing Primer Review: Does It Work? 6

Kilz Mold and Mildew is a great alternative if Zinsser Mold Kiling Primer is not available. Kilz and Zinsser are my two go to brands for primers and I use both of them on a weekly basis.

Kilz does not claim that Mold and Mildew will kill mold however while Zinsser does make this claim. Kilz states that this product is a great preventative. I use it in similar situations as Zinsser as I make sure the mold is already stopped before I prime an area.

You May Also Need:

If you are planning on using Zinsser Mold Killing Primer to prime out any rooms in your home, here are a few tools you may also need:

Frequently Asked Questions

Can I Use Zinsser Mold Killing Primer on Concrete

Block Wall Mildew

Yes you can use mold killing primer on concrete and block walls. Make sure to clean the wall first so the primer can properly bond.

Can I Use Zinsser Mold Killing Primer on Sub-Floors

Rustoleum says that Zinsser MKP is not meant for flooring or traffic areas. Personally, I have used it on sub floors after pulling carpet and before replacing the carpet.

When Can I Paint Over Zinsser Mold Killing Primer

You can paint over mold killing primer after 1 hour. Do not wait more than 72 hours before applying a top coat over this primer.

Does Zinsser Mold Killing Primer Smell?

All paints and primers typically smell to some degree. Most will not find the smell of this primer to be too strong, though a fresh air source during use is recommended.


Zinsser Mold Killing Primer is a great primer that is perfect for the DIY Painter to use in any high humidity area or where you have previously had a mold or mildew issue.

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