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Removing thin coat of shellac from an oak floor (use sandpaper or chemicals?)

Removing thin coat of shellac from an oak floor (use sandpaper or chemicals?)

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  #1  
Old 12-21-10, 12:22 PM
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Question Removing thin coat of shellac from an oak floor (use sandpaper or chemicals?)

Our 13í x 26í living room floor is 52 years old solid white oak in fairly good condition. Itís been protected by wall- to-wall carpet just removed. We want to finish living room with a clear finish (prefer water based urethane) to match the entry and dining room (finished a few years ago with some sort of unknown clear finish, probably urethane).

The living room floor had a moderately dark, thin finish (apparently the builder knew wall to wall was immediately going over the floor but applied a finish for protection). I tested this finish using denatured alcohol and confirmed it is shellac (i.e., itís tacky after wiping; hard scrubbing removes some of it).

Hope to sand floors using the U-Sand orbital sander from rental section at a local big box store. I want to avoid the hard to use drum sander and like the idea of U-Sand getting close to wall reducing the need for edge sanding.

Various online DIY advice and threads (along with rental clerk) talked about problems removing shellac finishes. Essentially shellac heats up, gets gooey and clogs paper quickly. Rental guy said with shellac you can use up a couple hundred bucks worth of orbital paper just getting the finish off. He said use a drum sander for shellac removal but I still want to avoid this.

The shellac is thin as far as I can tell (i.e., one coat applied 52 years ago). For a floor this size could/should I use chemicals before sanding?

If so which ones? Iíve heard denatured alcohol apparently works but takes a lot of elbow grease. Others are more expensive and dangerous. Of course getting rid of most but not all the shellac might help since Iím sanding anyway.

If I donít use chemicals and sand with a U-Sand machine should I start with 36 grit or 24 grit? If I start with a 24 grit what progressions should I use? Right now Iím thinking 24-40-60-80 grits). If I start with 36 grit Iíll go 36-60-80.

Lastly, most advice seems to indicate stopping at 80-grit paper if applying a clear finish. Is this correct?
 
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  #2  
Old 12-21-10, 01:31 PM
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I'm a painter not a floor guy but.....
I've never had any issues with applying an oil base poly over old shellac. I've never done any heavy sanding over shellac. Latex based coatings are bad to gum up when the sanding heats it up but I'm a little surprised that it would be an issue with shellac.

Do you know if the foyer/dining rm have a stain? or just poly? Waterbased polys go on a little milky but don't change the look of the wood any [except sheen] Oil base polys will deepen the colors naturally in the wood. Oil base also tends to amber some as it ages. If you are wanting a close match to the existing finished wood - you need to know more about it's finish.

Hopefully one of the floor guys will be along later with more info for you
 
  #3  
Old 12-21-10, 01:35 PM
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Here's the link to the thread from another forum with conflicting advice on what to do regarding shellac removal:

http://forums.finehomebuilding.com/b...ac-wood-floors

The last post (interesting but not responded to) was this:

"Open all the windows, shut off all the pilot lights and use alcohol..

Quick and dirty method is to get a string mop (foam won't work, it melts) dump a gallon in a bucket and swab the deck like a sailor.. get everything damp and keep it damp for a couple of hours.. then take a scraper and scoop up the residue. give the floor another mopping and scoop up the rest of the residue.. now rent a floor sander and you won't need those 24 grit or 36 grit paper. Light buzz and it'll be ready for your refinishing.. (wish I had an easy way to do that!)"


Unfortunately will be doing this job in January in a New England winter; not to sure about the open windows part!
 
  #4  
Old 12-21-10, 01:41 PM
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I'd try hand sanding a small area and see how that does. What is being discussed in the other forum is probably multiple coats of shellac from a full finish - that's not what you describe with your floor. I don't think you'll have the problems they discussed but you won't know until you try
 
  #5  
Old 12-21-10, 02:15 PM
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Originally Posted by marksr View Post
I'm a painter not a floor guy but.....
I've never had any issues with applying an oil base poly over old shellac. I've never done any heavy sanding over shellac. Latex based coatings are bad to gum up when the sanding heats it up but I'm a little surprised that it would be an issue with shellac.

Do you know if the foyer/dining rm have a stain? or just poly? Waterbased polys go on a little milky but don't change the look of the wood any [except sheen] Oil base polys will deepen the colors naturally in the wood. Oil base also tends to amber some as it ages. If you are wanting a close match to the existing finished wood - you need to know more about it's finish.

Hopefully one of the floor guys will be along later with more info for you
The foyer is actually unfinished oak that covered some old ceramic tile that was removed about 30 years ago. It was unfinished since it had been covered by carpet since.

The foyer is lighter than dining room which if the dining room had a stain (or darkening with oil based clear finish) is a very, very slight darkening. It's OK not to match perfectly since there is a transition bookcase on both sides in-between the LR and DR.

The living room floor doesn't need heavy sanding (e.g., no cupping, not too many major marks) but does need light sanding (e.g., need to fill holes from old carpet tacks; also fill a couple scratches and gaps). In addition still need to remove old dark shellac finish (it appears it was a shellac combined with stain although I don't know much about shellac).

Per previous post buying a gallon of denatured alcohol and using the "mop and scrape" method from link might be worth trying before I rent a sander. Will have about three weeks to paint walls, sand and refinish floors so at most I lose a day. Could experiment on the foyer closet which has the same dark shellac that covers the living room.

If I go that way this this scraper looks like the one to get. Probably should look into a gas mask too working with those fumes!
 
  #6  
Old 12-21-10, 02:24 PM
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Originally Posted by marksr View Post
I'd try hand sanding a small area and see how that does. What is being discussed in the other forum is probably multiple coats of shellac from a full finish - that's not what you describe with your floor. I don't think you'll have the problems they discussed but you won't know until you try
That's a good idea! (BTW, you know it's a good forum when answers and responses get written in parallel ).

Since the closet off the foyer has the same dark shellac as the living room I'll experiment there with hand sanding and the scraper without alcohol, along with denatured alcohol and the scraper linked above. Also have an old sort of heavy duty oscillating square shaped electric sander that I can try out.

Thanks,

walke
 
  #7  
Old 12-23-10, 10:04 PM
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Walke:

That's exactly the kind of scraper I was going to recommend you try using. It's sharp enough to scrape off gummy shellac, but not so sharp as to gouge the wood.

Technically, an "alcohol" is any compound that has at least one reactive hydroxyl group (-OH) bonded to a carbon atom.

Alcohol - Wikipedia, the free encyclopedia

If there's only one hydroxyl group, then it's a "monohydric" alcohol like methanol, ethanol or isopropyl alcohol. If there's more than one hydroxyl group, then it's a polyhydric alcohol, like ethylene glycol (antifreeze) or glycerine (more correctly, "glycerol") which you can buy at 99.9 % purity at any pharmacy.

Also, both ethylene glycol and glycerin are very slow to evaporate and have slmost no odor. So, I'd say it would be worth a shot to try using glycerine or antifreeze to remove that shellac. Try letting the glycerine sit on the shellac for longer; perhaps even overnight.

Both glycerine and ethylene glycol are clear colourless liquids. Both will evaporate completely without leaving any residue. However, antifreeze contains additives and also pink, yellow or green dyes so that engine leaks can be more readily identified, and I'd be concerned that the dyes from engine antifreeze could stain your wood. You might try using plumbing antifreeze, which is antifreeze poured into drain pipes to prevent the water in p-traps from freezing in cabins and RV's over the winter months. There'd be no reason to put any dyes or additives in plumbing antifreeze.
 
  #8  
Old 12-24-10, 08:20 AM
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Originally Posted by Nestor View Post
Walke: That's exactly the kind of scraper I was going to recommend you try using. It's sharp enough to scrape off gummy shellac, but not so sharp as to gouge the wood.
For tight corners I'm getting its baby brother too.


...Also, both ethylene glycol and glycerin are very slow to evaporate and have slmost no odor. So, I'd say it would be worth a shot to try using glycerine or antifreeze to remove that shellac. Try letting the glycerine sit on the shellac for longer; perhaps even overnight...

...You might try using plumbing antifreeze, which is antifreeze poured into drain pipes to prevent the water in p-traps from freezing in cabins and RV's over the winter months. There'd be no reason to put any dyes or additives in plumbing antifreeze.
I'll look for a small bottle of the glycerin (should be about 8 bucks for a quart) at a pharmacy and/or the plumbing antifreeze at a big box hardware store. I can't start the main job until a few days into the new year but plan to use the closet floor as my "screw up lab" right after Christmas using hand tools and small oscillating sanders I already have.

Also want to experiment with the finish coats in my lab/closet). Right now I'm leaning towards PRO Finisher Water-Base Polyurethane for the top three or four coats. Don't want to use oil based polyurethane because of the fumes given I can't open the windows for long in winter.

Per various online DIY recommendations I'll be using a sanding sealer over the bare wood (white oak) before I apply the top coat. If I stick with this product line I have two choices. First choice on half the closet is PRO Finisher Water-Base Sanding Sealer. Apparently this product doesn't darken wood very much. If the wood appears too light I'll try PRO Finisher Universal Sealer for Floors. This sealer supposedly gives the wood a rich tone (and it's shellac based - ironically what I need to remove first although it seems what I'm removing is combined with stain). Hope I can find something less than a full gallon for my experiments.

Thanks again for your help!

~ walke
 

Last edited by walke; 12-24-10 at 08:27 AM. Reason: fix typo, formatting
  #9  
Old 02-07-11, 08:09 AM
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Update with some lessons learned; hopefully others may find this useful.

I took off what appeared to be most of the shellac with hand scraping (the linked scrapers were excellent) and an odd choice of a remover, Odors Away Fabric Refresher. I originally looked for the suggested colorless anti-freeze and couldn't find it; also considered ordering glycol online. A clerk at a marine/boating store pointed me to a local Christmas Tree Shop that had the linked chemical for $1.69 per 22 ounce bottle. It was almost odorless and softened the shellac almost instantly; that said it seemed that simple scraping without using a remover was more effective as the shellac turned into a gummy mess with the chemical.

After scraping I appeared to have about 80% of the shellac removed so I thought I'd be fine. Used the
U-Sand orbital sander from a big box hardware store rental service. Started with 36 grit but the small amount of remaining shellac would gum up the sanding disks almost immediately. Went back to the big box store and got about ten boxes of 24 grit and used all of them with a helper chipping off shellac globs from the sanding disks from the last pass (the disks would glob up before the sandpaper was worn so we reused some when possible). I learned to move fast with the 24 grit to reduce heat build up on the disks, then go back to get the last bits of finish later. Once the shellac was removed there's no need to go fast with the U-Sand (unlike a drum sander).

Once the shellac was removed went to 36 then 40 then 80 grit (the store doesn't carry 60 grit; U-Sand's website seems to favor 36-40-80 anyway). Using the U-Sand was a breeze although I wouldn't recommended it if you have to take off a thick layer of deeply scratched or uneven wood (years ago I've used a drum sander for such a floor).

Used Pro Parks Universal Sanding Sealer after trying the Parks Water Based Sanding Sealer in a closet. The water based sealer darkened the white oak as advertised (specifically for white oak) in the technical documentation. Unfortunately it didn't look "rich" so I went to the Universal Sanding Sealer which ironically was shellac based! This went on very well (giving the wood a slightly amber color) so I hot coated (put the coats on about three hours apart) two coats of Parks Water Based Polyurethane. Let this dry for almost two days then did a light sand with 180 grip with a light orbital sander and put on the final coat. Floor looks very good; had few problems with bubbles, lap marks or dust/particles in the final finish.

Hope this helps someone.
 
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