removing varnish from sandstone

[piapiapiano]

Well, we went ahead and bought the house I mentioned in this post, largely because there wasn't anywhere else we could afford, and I'm almost too old to qualify for a mortgage. Waiting for permission from reclusive schizophrenic neighbour to fix the guttering and clamber about on his roof to repair our chimney stack. Waiting for quote from lovely local building firm for stripping off external render and re-attaching front wall to house. In the meantime, we've started chipping off all the plaster and cement internally. We've already found a blocked up fireplace that's filled to a height of 4 foot with damp soot. :shock:

What follows will be the first of MANY questions over the next few months, I expect.

What's best for removing varnish and paint from porous sandstone? The stone fireplace has been varnished, and it looks awful. We bought some Nitromors, but now I'm wondering if it will soak into the stone and stain it.

We're having to get a sandblasting company in anyway to remove a large area of spilt varnish from the concrete ground floor (spilt by previous inhabitants, who covered it over with a sheet of taped-down plastic while the varnish was apparently still tacky. I have no idea why they did this, but assume they had an accident while varnishing the stone fireplace. I have no idea why they did that either. There are lots of puzzles in this house). Would it be okay to clean sandstone with sand, or would it damage the surface?

 

[FamilyWiggs]

Hello PPP and welcome back. Congrqtulations on the purchase.

Cleaning any historic fabric with something as abrasive as sandblasting is likely to severley damage the substrate, and get a general thumbs down from the folk of this parish - this is especially true of something as fragile as a sandstone fireplace. At the very best you'll remove all aged patina from the surface, at worst you'll destroy what you have.

I can see you'll end up with 2 piles of sand - one from the blasting and one that used to be your fireplace!

Varnish seems to be an odd thing to put on a fireplace. Are you sure it is varnish?

Anyway, I would try the Strippers of Sudbury website - they have potions to remove just about anything from anything - and if you can send them a sample they can provide specific help . As ever, the advice is to try removing a bit from an unseen area first. In this case you could also try the floor first - anything that removes your varnish from the concrete floor is likely to work just as well on the sandstone.

Good luck - and remember to post us plenty of pics as you proceed!

 

[MattW]

Congratulations on your purchase

What's best for removing varnish and paint from porous sandstone?

Sandstone is very porous and the varnish is very likely to have got sufficiently deep into the stone that you may find it will be v.difficult to remove it all without first removing a substantial portion of the stone. Which leaves you a couple of decisions to make up front - will you like the look if you can't remove the last elements (it is could be pretty patchy as different areas will have penetrated to different levels) or are you willing at that stage to sandblast it anyway with all the problems that FamilyWiggs has highlighted?

I guess what I am trying to say is proceed with caution and if you decide to go ahead, try a stripper in a really unobstrusive area first.

 

[JoceAndChris]

Congratulations on the house- so sweet. Good luck with resolving all the difficulties that lie ahead!

We bought some Nitromors, but now I'm wondering if it will soak into the stone and stain it.

I think it might. I say this because where I've stripped wood doors with Nitromors and it's got on the stone floor it's left a permanent mark. I don't think it's the best product for the job - as has been remarked these people are very helpful:

http://www.stripperspaintremovers.com/I_want_to_remove.htm#11

I see they're recommending their product in conjuction with a pressure washer/ vaccuum attachment thing.

Sandblasting can have dire consequences - you should see my exposed brickwork, absolutely pasted by the previous owner!

As to why they varnished the fireplace- my guess is a fashion for varnish and a general disregard for/ignorance about historic fabric in the 50s/60s/70s.

 

[Penners]

Welcome back piapiapiano, and I hope you'll be very happy with your house.

I just want to echo what others have said above. Sandblasting would be very risky. The process is extremely abrasive (that's how it works!) and is likely to take off the paint plus a partial layer of the stone underneath. It could also leave the surface looking eroded. The areas most at risk are the sharp edges of the stone (known as "arrises") - sandblasting can round these off, which looks awful.

Strippers of Sudbury's website has a useful "I want to remove..." page, that will tell which of their products would be best for your needs.

Click here: http://www.stripperspaintremovers.com/I_want_to_remove.htm

 

[ilona73]

congrats on your purchase!
I recently stripped a sandstone fireplace in my dining room that had been painted black, the best thing i found that worked was a heat gun on gentle heat.Just enough to lift the varnish away from the sandstone gently .Its very time consuming will in all possibility take you weeks but i was really pleased with my results.

good luck

 

[piapiapiano]

Thanks, everyone!

So sandblasting is out of the question. I'm going to do a test patch of Nitromors on an out-of-the-way patch, just to see what happens. And thanks, ilona73 -- that's a good idea about the heat gun. I'll give that a try, if the Nitromors doesn't do the job.

And I've bookmarked Strippers of Sudbury, just in case the heat gun doesn't work...

 

[garnett]

Hello

I echo all the comments about sand blasting, but that is at one extream of the blasting spectrum. I remember when I did my conservation training, it was normal to start with the softest posible medium and work up. Crushed walnut shell is often used. It may also be worth a trial with the doff system. I find it great for removing paint from Bath Stone and no damage at all.

Find a bit that you can test on which won't be seen.

God luck

Garnett

 

[FamilyWiggs]

That's interesting Garnett. I presume it is still an abrasive method - but gentle enough not to damage the substrate? Sounds almost too good to be true - have you got any before and after pics you could post?

The advice to start gently and build from there is very sound.

 

[garnett]

Sorry - No photos but worth talking to a stone cleaning company as it is a common solution and they should be able to show you examples.

Here is a supplier's web site for the shell.

http://www.kramerindustriesonline.com/blasting-media/walnut-shells.htm

Garnett