DIY Chatroom Home Improvement Forum

DIY Chatroom Home Improvement Forum (
-   Painting (
-   -   oil based primer reacted with leftover mastic - wont dry - help (

amariemack 08-26-2012 07:39 AM

oil based primer reacted with leftover mastic - wont dry - help
we recently had asbestos tiles removed from the basement floor of our home. the contractors got up as much of the mastic / glue (black stuff) off of the cement floor as they could - but most of the cement floor was still covered with a layer of mastic when they were done. went to home depot and asked what we needed to do to paint over it... the salesman suggested an oil based primer, and then latex over it. we put down one coat of the oil based primer 2 days ago and it is still extremely sticky (and appears to have reacted with the black mastic - as it looks "dirty" - as if the white primer mixed with the black mastic residue and now look like dirty white paint)... we are at a loss as to what (if anything) we need to do now. or will this finally dry (a week, how long?) please advise if / what we can do - or if it will eventually dry so we can put down the latex paint over it.

Brushjockey 08-26-2012 07:58 AM

The rocket surgeons at the box store strike agaiN!

The solvents in the oil paint are the same solvents in the mastic, so it is dissolving the mastic.
One question- tell us what you are ultimately trying to do-
just seal in the mastic to carpet over, or how are you wanting to finish the floor?
The answer will determine how much more effort you should put into removing the mastic.

amariemack 08-26-2012 08:35 AM

we weren't trying to remove the mastic at all... just wanted to paint over it to seal it and then have a clean smooth(er) not-so-hideouse surface in the basement space. this is something we weren't expecting after the conversation i had with the home depot guy explaining the entire situation to him. will it ever dry? we were expecting it to dry and them put 2 coats of latex over it (dark gray) to cover the floorspace.

Brushjockey 08-26-2012 08:56 AM

You now have partially dissolved mastic. It will maybe dry, but it will not be good.
I would recommend getting a blade scraper ( like an ice scraper ) on a pole, actually wetting it more with mineral spirits and scraping off as much as you can. Be careful to dispose of carefully- let it harden up outside- ventilate well while doing it.
Then put a fan on it and let dry.
What to seal it with... Hmm. Def not something with a petro solvent base.
Maybe use a waterborne floor paint that is epoxy reinforced. Much better than just " some latex paint" might have the possibility of not flaking off right away..
You will only have as smooth a floor as you put in effort to remove the stuff.

amariemack 08-26-2012 09:24 AM

we didn't want to remove / scrape up the mastic at all... it is a very large floorspace that we are dealing with. will it dry within a week and then we can just paint over it? or will it stay sticky / tacky forever? at this point we really are hoping it will dry and we can paint over it - which is all we wanted to do in the first place... (mind you - we're 2 women - my mom is 68 and we just wanted to cover the black mastic to make it smoother and not so ugly looking). is scraping going to be the only alternative for us at this point? the parts where there was no mastic look clean and are indeed dry....

Brushjockey 08-26-2012 09:39 AM

Put a fan on it and wait.
I think it should dry/ harden up after all the solvent gets out of it.
But what to put on after is still a consideration.
There a a couple that chime in here that would have a better idea. But because painting over mastic, particularly on floors would never be recommended- its not like there is and easy answer.
You have an unstable surface, that is rough, and being walked on.
not just anything can stand up to that.

amariemack 08-26-2012 11:10 AM

right now we have 2 box fans going and we turned the dehumidifier on hoping to dry it out... if / when dry - can we continue with the plan to put a porch and floor enamel on it? water based.... we're just looking to salvage at this point and get a dry basement floor back. thank you so much for your comments today too.

joecaption 08-26-2012 11:27 AM

I just can not see any form of paint or sealer holding up to foot traffic or even coming close to looking good over old mastic.
It could have been tiled over before the paint went on but now that's out.

Brushjockey 08-26-2012 11:28 AM

The solvent isn't water- so the dehumidifier isn't doing anything directly to it, but if the basement is real humid the thick air slows down the evaporation- so in that way it might help.
Im hoping a guy named ric knows paint ( and he does) chimes in.
You will get some more opinions- so be patient. You're drying it- so not much more you can do right now anyway.

user1007 08-26-2012 11:31 AM

You've a couple problems going on now. First, as mentioned, the solvent based primer is melting into the leftover mastic. Second, and potentially more serious is the oil primer is likely to react badly with the concrete alkalinity in short order even if it does dry and it will fail underneath whatever you try to put over it.

You should not have been encouraged to skip the removal of at least the majority of the mastic if you wanted to paint the floor. And primers are usually not used on floors because they are not built for the wear and floor paints are self-priming. There are, of course, some two step industrial floor coatings that involve an etching/primer/sealer.

At this point, and I know you do not want to do so, you should do as advised, get a scraper, and get as much of the mastic up as you can. Then use an appropriate solvent to get almost all of the rest.

Follow with something like Benjamin Moore's Acrylic Floor, Porch and Floor Paint which is epoxy reinforced. It is self priming and should go over what little residue is left when you are done scraping. For that matter you could use the oil based floor paint product if you prefer. It will not react with the concrete and is urethane reinforced.

At this point, you might want to consider some sort of inexpensive carpeting over the top of the mess if you absolutely do not want to get the mastic and primer up. You do have a fair amount of work ahead of you. The good news is the mastic is gooey and I think you will find it will go scrape off fairly fast. Make sure you have adequate ventilation working with the solvents.

You certainly have reason "to have words" with the idiot at Home Desperate who gave you such terrible advice even if he is just minimum wage and is not expected to know anything about products. Get your money back from them at least and make a scene if you want.

And not to scold, but from now on buy paint from a paint store where you should get coherent advice.

joecaption 08-26-2012 11:41 AM

A mastic remover like this may be a whole lot safer to use.

user1007 08-26-2012 11:48 AM


Originally Posted by joecaption (Post 996784)
A mastic remover like this may be a whole lot safer to use.

Yeah I thought of that but what she has is already softened. And right now she has more than mastic with the primer added in to make a muddy, sticky, gooey mess. I honestly do not know if the mastic remover will work on the combination? It could just make things worse?

I would have to consult a data sheet or ask for customer service advice. Or see what real paint store or janitorial or floor chemical folks suggested. I would not seek out an orange aproned person (but then you all know I do not shop in such places). Stuff like it (do not know this brand) works great but given recent experience with HD I wouldn't get it from them! Something like it is what should have been recommended in the first place.

chrisn 08-26-2012 04:53 PM

Hey, the mastic has to be delt with somehow, Would not some kind of cheap plywood type product over top the whole mess be cheaper, faster?They are going to paint it anyway, right?:huh:

amariemack 08-27-2012 08:55 AM

yesterday afternoon we bought the scraping tools, etc - and began to scrape up the sticky mess... spent 4 1/2 hours last night and will be spending today doing the same. backbreaking work. we'll try to get up as much as we can and hope what's left hardens enough to paint over. thank you for all the comments and guidance on this. we were really at a loss as to what was happening and why.

Brushjockey 08-27-2012 09:22 AM

Sorry this ended up to be more work than you wanted- but sometimes doing it right is worth is in the long run- just pace yourselves.

All times are GMT -5. The time now is 02:35 AM.

vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
User Alert System provided by Advanced User Tagging (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.

Search Engine Friendly URLs by vBSEO 3.6.1