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Help! I sprayed latex on MDF - peterbud - 03-04-2019

I went to the local Benjamin paint store and inquired what would be the best primer for MDF board. He suggested Zinsser Primer to be the best choice. So, I sprayed two diluted (2:1) coats on a desk I just finished.  Now, while browsing on another subject I hear that a water-based primer shouldn't be used on MDF board? Suggestions?

RE: Help! I sprayed latex on MDF - fredhargis - 03-04-2019

Wait until it dries and see if you have any damage. MDF swells a lot in the presence of moisture. I'd guess your paint store guy doesn't know what MDF is. If there is no swelling, you have nothing to worry about...if there is you're only recourse that I know of is to get some more MDF and do it over. It's possible the paint guy meant to suggest Zinsser BIN primer....it's shellac based and has only trace amounts of water.
PS: welcome to the forum!

RE: Help! I sprayed latex on MDF - jteneyck - 03-04-2019

(03-04-2019, 01:31 PM)peterbud Wrote: I went to the local Benjamin paint store and inquired what would be the best primer for MDF board. He suggested Zinsser Primer to be the best choice. So, I sprayed two diluted (2:1) coats on a desk I just finished.  Now, while browsing on another subject I hear that a water-based primer shouldn't be used on MDF board? Suggestions?

Even if it did swell a little, I think it'll be fine after it dries really well.  If you're lucky it'll be fine.  If not, you should be able to sand it flat and smooth again and start over - with BIN pigmented shellac based primer.  Great stuff under most paints and on many substrates.  Fred's right that it could swell and delaminate the MDF, but I think only in the most extreme situation.  


Let us know.   

John

RE: Help! I sprayed latex on MDF - Phil Thien - 03-04-2019

It will be fine, I use water based products on mdf w/o sealing without much difficulty.

RE: Help! I sprayed latex on MDF - peterbud - 03-04-2019

They sold me Zinsser "Smart Prime" (photo attached). Claimed he was familiar with MDF! The can says "Primer for all projects... sticks to all surfaces... performance of oil"  So it sounded like I was in business.  So far, and I only painted this yesterday, there doesn't appear to be any abnormality. At this point, unless there's something really noticeable, I'm just going to put on the finish latex coats and see what happens. There's a fair amount of routing involved, so I don't think there are many options to do anything with the coat on there now. The project took me a number of weekends. Need it as a gift for my daughter. There'd be no time to start over. If it doesn't work out, I'll give it to her and tell her this is just a "prototype" and the real one will be coming soon! 
Yes

Thanks for the advice and the welcome to the forum. Thanks for having me. This is why I love forums. I don't join very many, but when I do, they are always helpful, but not as quick as this one with a response. Thanks.

Warmest regards,
Pete Budraitis

RE: Help! I sprayed latex on MDF - Phil Thien - 03-04-2019

So what are you top-coating with?  Latex what? And what is the project?

You should be aware of things like blocking, which is the attribute that causes latex paint to sort of remain tacky and stick to thinks with which it comes in contact.

RE: Help! I sprayed latex on MDF - fredhargis - 03-05-2019

Phil made a good point about blocking, do not use a type of wall paint (although some are now 100% acrylic latex, they may not be a problem) to avoid everything sticking to it that may touch it.

RE: Help! I sprayed latex on MDF - Cooler - 03-05-2019

I've used water based paints on MDF with no issue on the factory surfaces.  The cut surfaces need to be treated or they will raise the "grain".  To  get a really nice finish on the edges I first apply grain filler (Parks which is designed to fill the grain in open grain flooring) with a rag like you would apply shoe polish.  After about 30 minutes I lightly sand the edges and dress them with Sealcoat.  

At that point you are good to go with water borne paint.  

The Parks product applies easier, dries faster and sands easier than any other that I have tried.  It is available in the flooring department at Home Depot (and probably most big box stores).

[Image: 614ghQJRfzL._SX425_.jpg]

RE: Help! I sprayed latex on MDF - peterbud - 03-05-2019

I should have found and checked this forum before I started the painting project. I definitely will be more prepared next time with these excellent tips. I'll let you know how this project turns out, doing what I could do now.

— Pete

RE: Help! I sprayed latex on MDF - CLETUS - 03-05-2019

I wasn't familiar with this product... 

I found the instructions amusing... for tough stains they tell you to use shellac based BIN primer. I guess I'd stick with that...
Raised

Oh, and thinning instructions are no more than 10oz per gallon.


https://www.rustoleum.com/~/media/DigitalEncyclopedia/Documents/RustoleumUSA/TDS/English/CBG/Zinsser/SPM-01_SmartPrime_TDS.ashx