# Blasting to remove paint from cinder blocks in a basement



## JoeT

My situation is similar to a thread on another forum: http://www.contractortalk.com/f95/painted-cinder-block-walls-79883/#post954974 from 2010. I have real cinder block and not concrete block. You can actually see the steel slag cinders in the blocks. 

I've tried removing the paint using some of the best paint strippers out there without much luck: Peel Away 1, Peel Away 7, Smart Strip, Smart Strip Pro, and Lightning Strip. 

I tried 3000 psi pressure washing with very poor results. 

So now I'm thinking blasting (as in media blasting).

I thought I'd run an inexpensive test to see if blasting even offers hope. If it showed promise then I'd be looking to make an investment in a pressure pot and a decent compressor. 

For my test I picked up a a 'blaster gun' from harbor freight http://www.harborfreight.com/gravity-feed-blaster-gun-93221.html#pr-header-back-to-top-link and rented a 4.9 [email protected] compressor. Unfortunately the test was a failure. It barely removed any paint. I was using 40/70 grit glass media. I made sure the glass was actually being blasted out and tried holding the gun at different angles and distances. 

Would using a larger grit size have made a difference? I wanted to post this on the contractor talk forum but they don't allow DIY posts there.


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## Gary in WA

To what end result? Gluing foam board on?

Gary


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## stadry

IF you want to ruin either conc or cinder blks, sandblast 'em,,, won't make an difference what media you select - corn cobs, talc, 00 sand, glass beads, walnut shells, etc.

the surface you're blasting isn't uniform in strength so you'll wind up w/holes all over the f'n place,,, get an aurand deck scaler if you must OR attach frp panels to the wall

this is just my opinion based on experience,,, we own these machines for the same reason [ no financial interest / other companies make 'em / eBay's a good source ]


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## wkearney99

What is it you plan on doing to the wall once the existing paint is removed? As others have pointed out, it's probably only going to make things worse if you try to use a media blaster on it. Possibly a LOT worse.

So tell us what you're planning on doing with it once it's cleared.


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## Canarywood1

See if anyone in your area use's co2 or dry ice blasting,and ask if they can do it,i know it will remove paint from metal and wood,and there's no mess to cleanup.

https://www.youtube.com/watch?v=OJ9jCenZ1YQ


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## stadry

now we're getting into BIG $$$ - you can also use baking soda blast media but @ what point do you safeguard your wallet ? cinder block's not uniform strength product so you'll get holes/canyons/mountains no matter what media you select :yes:

at lease w/aurands, you can prep a sufficient %age area to gain & secure long live adhesion :yes:


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## JoeT

Thanks for the replies and the questions. 

The end result is to have a basement that is nicer than just painted blocks. So getting the existing paint off those blocks, which are full of efflorescence and discoloration, has to be the starting point to figuring out what can be done next. If it's impossible to get the paint off then there is really no point to do anything beyond repainting the blocks. If I can get the paint off then I'll put on of some type of vapor barrier coating next. But that stuff won't work unless the starting point is unpainted concrete block. 

I took all the paneling off the walls last year. They were nailed to 1/2" furring strips, which were then nailed directly into the painted blocks. This was done by the previous owner decades ago. I guess back in the 60s that was how you finished a basement. Upon pulling the paneling off I discovered areas with crazy amounts of 'snow' (effloresces) growing on the blocks. In some places it was an inch thick!. On the interior of some of the paneling I discovered areas of powdery yellow mold. Most of the paneling had some amount of delamination occurring on the lower edge. All this points to water vapor and that was coming through the blocks.

In the seven years I've been in the house I have never seen any standing water and the previous original owner said he never saw any either (he was 93 years old when I bought the place). So hopefully for the past 60 years the extent of the moisture problem down there was just your typical high humidity in a basement with the associated funny smells. Running a dehumidifier constantly kept it almost pleasant down there but there was always a little bit of funny smell.

If I can as a starting point treat the interior of the blocks then I can start thinking about the next step. Putting up some foam board and drywall on top would sure be nice. 

If money was no object I'd hire someone to do a proper down-to-the-footer exterior excavation and water proofing. But that costs tens of thousands of dollars which I don't have. 

I was thinking about soda blasting. It sounded promising but I ran some numbers and it looked like it would require a ridiculous amount of baking soda. I thought glass media could make more sense since it will be more aggressive than soda and it can be run through the blaster several times, instead of just once like soda, thus keeping the cost of the media down.

I wish there was someone in my area that had a high power mobile set up that would actually consider doing a job in a basement. Maybe I just don't know who to ask...


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## Canarywood1

Sounds like it's mainly the efflorescence that's bothering you not the paint,if that's the case this link may provide you with some help.

http://www.aldonchem.com/popup-ab-efflorescence.htm


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## JoeT

Thanks Canarywood1. That aldonchem link is giving an angle to what might be going on that I never heard of before. I did have extensive efflorescence blooming and per the article that is the worst kind. That might have something do with why it's so hard to get the paint off (if it is indeed paint). Another product to try and with that some new hope.


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## stadry

not sure what you're looking for since the end product of any media blast will look like a teenager w/horrible acne :furious::furious: try googling up ' dry ice blasting cleveland ',,, found several guys but @ what point do you say ' how much $ do i pour into this project ? '

don't know why aurand's hand scarifiers haven't resonated but its your house & your $ - 100sf/hr or more - you'd be done in the time you've been in this forum :whistling2: we own 'em & use 'em to make a living

woody, is aldon a mfg OR distributor/re-packager ? prosoco's another source of ' stuff ' :yes:


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## joecaption

Unless this problem is also addressed on the outside (waterproofing) it's just going to come back.


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## Canarywood1

woody, is aldon a mfg OR distributor/re-packager ? prosoco's another source of ' stuff ' :yes: 
__________________

They are a Mfg. been around for 40/50 years.


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## jomama45

joecaption said:


> Unless this problem is also addressed on the outside (waterproofing) it's just going to come back.


If the paint's gone, the walls will be allowed to dry to the interior, like they were intended to in the first place.

Not sure if you're trying to say that removing the paint will bring the paint back again????????? :huh:


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## JoeT

itsreallyconc, Never realized there was such a thing as a hand held scarifier and am intrigued by what one might do. Google told me a little bit about 'aurands' and it's impressive. Didn't see any on Ebay. Seems like an uncommon tool. Does not look like anyone rents them in my area (Cleveland, Ohio). But I'll keep looking into this. 

No offense to anyone out there but for the benefit of everyone who keeps wondering why I'm doing this: I'm exploring all options at this point because the obviously 'right way' as I mentioned earlier is insanely expensive. If the wall looks ugly and beat up after I'm done, but I can seal it and then cover it up as a finished wall then who cares? As long as the structural integrity of the blocks are not affected then I don't care. If the end result is not as good as doing things the right way but is 20 times less expensive and is 'good enough' then why should I care? I don't really have water problem but a humidity problem. Why can't I at least partially address it by taking steps to block the transmission of the water vapor through what is normally vapor permeable concrete cinder blocks?


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## stadry

eBay - item # 121212508321 - or search ' aurand ' &/or ' scarifier ',,, aurand.net [ no financial interest ],,, we own/use 'em for just what you're trying to get done & also trim down & resurface conc - MUCH less dusty than grinders :yes:


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## JoeT

itsreallyconc, Well I just bought item 121212508321 on ebay (one of three available). If this thing works I'll be floored and will be only wishing that I had known about this a year ago. I've spent so much time, effort and money trying to solve what seems like an impossible problem. I'll let you know how it goes.


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## JoeT

*Aurand scarifier progress*

How long should the cutter blades last? I only did about 40 blocks and here is what the cutter blades look like now. These are were new cutter blades that came with the scarifier. It feels like the effectiveness of being able to remove the material is doing downhill fast at this point. Sometimes I'm getting sparks off the surface of the block. I guess that is because of the steel slag embedded in the cinder blocks. Some blocks seem to get cut pretty easy while others are barley getting scratched. I don't think I'm putting much pressure on the cutters and am trying to just let them do the work. But not much happens unless I start adding pressure. 

It would be an understatement to say this makes a mess. I took some measures to have all the dust contained but it's not enough. The entire work area is enclosed in plastic sheeting (ceiling too) and there is 1100 CFM fan exhausting the dusty air out the window. 

I guess I better buy the vacuum attachment for this thing. I'm seeing the cutter blades go for about $70 a set. At this rate I'll be spending some serious money to do all the blocks. But I don't see any other choice.


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## stadry

40 x 16 x 8 / 12 = 35sf,,, think you should be getting more, too,,, try using carbide cutters - steel's not working well enough imo

you're right - let the tool do the work,,, chipping gun & 12pt/16pt bushing tool's another possibility but i still favor frp panels


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## wkearney99

I'm still puzzled as to what the end game is going to be.

It's likely there's still going to be the external moisture issues, as nothing's been posted here regarding efforts to abate them. All this effort to peel off the inside mess while doing nothing to prevent it from coming right back again. When you see signs of problems like this there's really no better effective long-term way to solve it other than exterior remediation. Otherwise the problem WILL come back again. Now, maybe it might not come back within a given timeframe, like during the time it takes to flip a place but that doesn't sound like what you're doing.

Think about it this way, ever gone down a basement and commented, gee what a nice looking block wall? So why bother making it look nice? Get it roughly cleaned and properly cover it back up again. As in, a stud wall, insulation proper for your area and a wall covering (frp, drywall, etc). While meanwhile solving the exterior water problems once and for all.


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## JoeT

Hopefully will find that cutter blades I'm using are cheap ones and not carbide steel. And then find getting carbide ones will fix the wear problem. 

Seems weird to quote myself:



JoeT said:


> No offense to anyone out there but for the benefit of everyone who keeps wondering why I'm doing this: I'm exploring all options at this point because the obviously 'right way' as I mentioned earlier is insanely expensive. If the wall looks ugly and beat up after I'm done, but I can seal it and then cover it up as a finished wall then who cares? As long as the structural integrity of the blocks are not affected then I don't care. If the end result is not as good as doing things the right way but is 20 times less expensive and is 'good enough' then why should I care? I don't really have water problem but a humidity problem. Why can't I at least partially address it by taking steps to block the transmission of the water vapor through what is normally vapor permeable concrete cinder blocks?


No point to putting up walls until I have some assurance that water vapor coming through the porous blocks to the interior can be reduced. I have a humidity problem not a water problem. Easy to say spend the $10 - $15K for the drastic fix when it's not your $$.


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