safe efficient ways to clean used brick?

Our son is wanting to reuse the brick that slumped off of a wall of his house and is trying to clean it up first.
Does anyone have some ways to clean up a lot, as in hundreds, of bricks? They are separate individual bricks, just have quite a lot of cement still on them.

They are trying several things, some with power tools and some with hand tools...it's possible, just a slow go.

Thanks for any and all suggestions

Hi Judith;
I'm sorry to say that I have never found a fast method of brick cleaning.
A lot depends on how well the concrete bonded.
A side grinder with a masonry wheel is the most efficient I have found BUT you need a half mask respirator  and where ever you do this will be a horrible dusty mess.
A rock hammer with a flat end works if the mortar has not bonded well.  The danger is splitting the brick.
I have done quite a bit of brick rescue...  dirty , can be dangerous work.
If you love old brick like I do its a labor of love!
Tell him he is doing a good thing and carry on!

I have only done this a couple of times with a hammer and chisel.  Yes, and do be prepared to break a few bricks.

Thomas speaks of protecting the lungs ... protect the eyes too.

I too have spent many-an-hour removing cement mortar from both clay and cement bricks with no other advice than what has already been given.
I found a vice to be somewhat helpful for those bricks where many whacks were needed and could use both hands for that.
"A labour of love" as what Thomas said was the main thing that kept me going!
Seeing your project being created in front of you with each brick and knowing they aren't just being tossed into a landfill was also very helpful.

I believe that hydrochloric acid is used to clean cement off bricks. You would need to get the bulk off mechanically, but finishing with HCL will give you a lovely final clean surface.

I use a tomahawk.
Its
Its fast , effective and not dusty.
Personally I would never use  an angle grinder, fingers and lungs may be damaged.
As for HCL dilute it to about 10% HCl and water.
BECARFUL YOU NEED TO ADD ONE TO THE OTHER AND I CANNOT REMEMBER WHICH WAY IT IS.
Also wear old cloths, splashed of the HCl will eat holes in any clothing.safe and comfortable.
I place the brick on a support and swing the tomahawk down to just above the join between the mortar and the brick.

thanks everyone!

I'll pass ideas on to him and his wife....they have tried a few of them already and I think have resigned themselves to a long tedious job that will be worth it in the end.  

When our boys were young we had lots of 'tedious' things going.  
One project was a lot of old oak boards from tearing down a building...full of nails.
Pulling the nails was the easy part compared to straightening them for reuse...cans and cans of them.
They both helped and at the time had fun....that is my memory of course, I'll have to ask if that fits with theirs

John C Daley wrote:
As for HCL dilute it to about 10% HCl and water.
BECARFUL YOU NEED TO ADD ONE TO THE OTHER AND I CANNOT REMEMBER WHICH WAY IT IS.

Good point.

You need to add the acid to the water, not the other way round.

Combining water with strong acid generates considerable heat. Adding a small amount of water to a strong acid can make the acid literally boil. Not good.

Adding acid slowly to a large volume of water means the heat dissipates quickly into the water and you avoid the potentially violent reaction.

Michael Cox wrote:

John C Daley wrote:
As for HCL dilute it to about 10% HCl and water.
BECARFUL YOU NEED TO ADD ONE TO THE OTHER AND I CANNOT REMEMBER WHICH WAY IT IS.

Good point.

You need to add the acid to the water, not the other way round.

Combining water with strong acid generates considerable heat. Adding a small amount of water to a strong acid can make the acid literally boil. Not good.

Adding acid slowly to a large volume of water means the heat dissipates quickly into the water and you avoid the potentially violent reaction.

Absolutely correct.
I teach high school chemistry.
Every year I put this on the board.

Water On Acid = W(h). O.A. = WHOA

So, don't put water on acid.  Put acid on water.

Update...

They are halfway through the bricks the slow tedious way and now working on rebricking the foundation....the siding is pine from son's bandsaw mill.

How or why did the bricks fall off?
Is it an older home?

Howdy,
I've used this, when someone gave me a bunch of used fire brick.
need air compressor
peace,rc

randal cranor wrote:Howdy,
I've used this, when someone gave me a bunch of used fire brick.
need air compressor
peace,rc

That is the way I would do it too. But that is because I have the tools to do it that way.

What would speed that effort along is some kind of shavehorse like affair to hold the brick rock solid when the mortar is chipped away.

That is my project before the snow starts to fly. Alternating between planting garlic and brick cleaning. Have been scouring the country side for bricks for years and I have quite a few pallets of bricks collected these will be for my new chicken coop.  Hopefully this will be rat proof!  I think i will clean and  do some mortar as long as the temps stay above 2C.. They are not all the same size so this should be interesting. I’m good at improvising. I might just throw some favorite rocks in the mix too!  

Hey,

careful with sand blasting you may ruin the bricks.

The advise above is good but keep the dust down by wetting the bricks, a pressure hose is a great idea as well and if you do not have a pressure hose you also have a thumb and can reduce the size of the nozzle in the hose thus increasing the velocity of the water.

this will save you having brown crunchy mucus up your nose.

The tomahawk, No, just no yes it may work but a cold chisel and hammer is going to protect the bricks better, as well as they have a shorter apex and you will burn less steel through the process!

with a brick chisel and pound hammer I have pulled 1000 brick walls apart in rain, so I have natures cleaner on my side. and then I just wet them and work them parallel with a wire brush, and a few chisels. it can be done in a weekend with out power tools.
to make them pristine you kind of need to gurney them and use vinegar or brick cleaner or clr works.

1000 bricks is just 1 brick than 1 more, and then repeat until you run out of bricks to do!

Better living through chemistry!

But when all else fails, brute force and ignorance works for me.

OH wow! Something Im an expert on - that I can give my opinion. I used to clean bricks for a living in NZ, there is a whole industry in recycling bricks.
We use a hatchet. That chops off the old mortar very easily. One must grip the brick tightly with the left hand while using the right to knock dirt and mortar off, all without slicing off any fingers and while avoiding blisters.
Gloves are recommended.  
I used to sit in an old car seat and have tons of bricks dumped around me...
We got 20 cents per brick for cleaning and the boss sold them for 1$ each ! This was 1995

A pallet was 500 bricks -  that was 100 bucks - you could do 3 a day if you were good. 5 if you worked from dawn to midnight because the bricks were running out and other people were cleaning them too !

That was alot of money... A 1 litre of strongbow cider was 3 $ and a good pie was 2 $

Anyway... im getting off track here...

Use a hatchet.

My own experience is that wet bricks clean more easily. So do bricks from a chimney which has been on fire.
I favor using a hammer and brick set, a one-sided chisel. You will break some bricks. You don't need to make a long swing, just tap hard. Wear something over your eyes.

I use a hatchet too. Works quickly.

Phil Swindler wrote:

Michael Cox wrote:

John C Daley wrote:
As for HCL dilute it to about 10% HCl and water.
BECARFUL YOU NEED TO ADD ONE TO THE OTHER AND I CANNOT REMEMBER WHICH WAY IT IS.

Good point.

You need to add the acid to the water, not the other way round.

Combining water with strong acid generates considerable heat. Adding a small amount of water to a strong acid can make the acid literally boil. Not good.

Adding acid slowly to a large volume of water means the heat dissipates quickly into the water and you avoid the potentially violent reaction.

Absolutely correct.
I teach high school chemistry.
Every year I put this on the board.

Water On Acid = W(h). O.A. = WHOA

So, don't put water on acid.  Put acid on water.

And, once more for those on in the back... The mnemonic I learned was:
Acid Into Water = Aren't I  Wise.
Water Into Acid = Wise I  Ain't.

I prefer the chisel and hammer, for more control. But a well-directed bricklayer's hammer can be faster, if a few broken ones can be tolerated.
For the OP's situation, a renovation of this kind demands that there be as few broken as possible, unless there is a stash left over from the original build tucked away in a basement, or crawlspace. (My mom actually found spare bathroom tiles in the garden below the bathroom window, since the leftovers were just tossed out, and buried!) A.) It always helps to find a stash, so check around B.) Always plan for an inconspicuous spot to use those broken ones if you must! or if you get a different lot that won't match exactly.

John C Daley wrote:How or why did the bricks fall off?
Is it an older home?

Yes it is an older home, early sixties...not sure why the brick slumped off though?
Just on that back wall and the rest is solid.

Howdy
When I was younger and learning "do it yourself" building, I tried making mortar using river run sand. It worked but developed cracks.

Maybe the mix was a tad off on the old house mortar, or curing on the back wall was different?  I know if you have the right local ingredients you can make your own cement/mortar, but there is a right way. Old timers were able to do it. Some really nice old stone houses in southern Missouri.  Just a thought...

Judith Browning wrote:

John C Daley wrote:How or why did the bricks fall off?
Is it an older home?

Yes it is an older home, early sixties...not sure why the brick slumped off though?
Just on that back wall and the rest is solid.

The bricks slumped because the foundation had moved...so all of that repair was first and then the brick work.