Sunday, November 1, 2015

Stairs Refinishing: Stripping, Staining and Poly

The maple stairs that I had installed years ago got a bad finishing job by the contractor's son in law. He was careless and didn't follow any of the standard practices for staining. Specifically he did not:

Sand the wood. Sanding opens the pores to accept stain and results in a smoother finish.
Clean the wood with mineral spirits prior to staining (some oil/food/grease from foot traffic resulted in ugly marks where the stain did not absorb)
Wipe off excess stain properly. He left it on way too long (the can says 5-15 minutes). And he didn't wipe it off evenly, leaving odd patterns.

He also failed on the polyurethane coat. He was rushing the job and applying the next coat before the first had dried. This resulted in an inconsistent finish that was rough and full of brush marks. Of course he didn't sand between coats or thin the final coat.

I had some time off from jobs and it bothered me enough that I decided to try to fix it. I started with some test pieces to see if I would be able to remove the stain. Here's a test stair tread where the stain was left on to dry on half the board



Once this stain dries it's not coming off no matter how hard you wipe with mineral spirits. Your only choices now are stripping or sanding. While sanding seems like the easier, less messy option, it would have required way too much effort to get the corners and details on the stair post, not to mention removing wood on an already thin veneer (post). If I could have hit all surfaces with an orbital sander, I'd certainly consider sanding, but by hand, no way!


Here you see the citristrip at work. It foams when it reacts with the poly. then you simply scrap off the flakes. It took about two applications to remove the poly.



Once it no longer foams, the poly is gone and I used a scotchbrite to work the citristrip into the grain to remove the stain. You can see it's darker where the stain was left to dry and this area required more scrubbing.


And finally it's looking almost like the original. Since this was a test piece I wasn't concerned with removing all the stain, only that I could remove the stain where it had dried, so ignore the area of stain on the top. It takes a while for the citirstrip to dry, during which time it may look like some stain is still on the board but it was just wet in my case. Fans are great to use to speed drying, or in my case I could leave the piece in the sun.


Here's my stained test piece (not the same tread as above). I experimented with frog tape to see how well it would hold a line. Here you can see the variations in the wood will dictate how the stain is absorbed, with the center portion of the tread being a different piece of maple and darker.

I started by stripping off the polyurethane with Citistrip. Citristrip is superb at removing polyurethane and also does a decent job removing stain. I found that a scotchbrite pad in the direction of the grain to be very effective with removing the stain. The best thing about citristrip is it doesn't have bad voc odor; actually it has a pleasant orange smell. I wore heavy rubber gloves and it did wear through the fingertips after the 3rd coat. I got it on my skin a few times and no problems after washing it off, but I wouldn't want it exposed to my skin for any longer.

I was only redoing the post and treads since the handrail was actually not screwed up, somehow. I used frog tape to keep the citristip off the handrail but despite taping it very tight some did ooze though. Fortunately it was not very noticeable and I wiped on some stain to blend it in.

After stripping, I used mineral spirits to remove the citistrip. Citistrip recommends the odorless mineral spirits but the reviews for that product are dreadful so I used the good old stuff. Citristrip dries to a white powder in the corners but comes off with a scotchbrite or plastic scraper and a toothbrush is helpful too. If you have lots of corners or detail this can be a pain.

I used a wood conditioner on the treads. Typically wood conditioners are recommended for soft woods (e.g. pine). I was working with hard maple which has a tendency to get blotchy, so wood conditioner is recommended. It partially seals the wood so it will accept less stain and you end up with a slightly lighter color, however you can reapply to get it darker.

Make sure you wipe off the excess stain, or it will dry on the wood and look like you painted it instead of staining. At best it will result in uneven color. Before a wiping cloth gets close to saturated, replace it or you'll just end up pushing stain around and it will dry in the most unfortunate of ways. You can wipe excess stain off with mineral spirits, but only before it has cured. I did an experiment and tried to remove excess stain a day later and it simply would not come off, but wiping with mineral spirits an hour or two after application proved successful.

What I've learned. I hate stain! Stain can look great but there are some many variations in wood that can be highlighted by stain and result in a uneven finish. Once the stain goes on you're potentially looking at a lot of effort to remove if it doesn't look good. I read several stories of bad stain jobs where they just gave up and painted rather than try to strip and refinish. Another consideration of staining is dents and dings will be more visible since they will show the natural wood color if the scratch/dent is deep enough. Lastly when refinishing, if you apply stain over dings or scrapes, they will absorb more stain and show up darker. In hindsight I should have skipped the stain and just applied poly to the natural maple -- it would have looked fantastic!

Polyurethane tips. Use a natural bristle brush, not nylon, and use a quality brush. In my experience cheap brushes drop bristles on the poly which are challenging to remove afterwards  Don't over apply. Work it in with long light and slow sweeping brush movements. If you are dealing with vertical or angled surfaces it can form drips and often you won't see these until it's drying. I've had some luck with removing drips using a cloth that is wet with mineral spirits but you have to catch it before it's hardened. If you do this make sure the rag is only slightly moist or you will end up with more runs! You may see bubbles on the first/second coats. This is ok and they can be sanded off (wait 12 hours or mfg recommendation before sanding). On the final coat you can thin the poly with mineral spirits (2 parts poly to 1 part mineral spirits) and wipe or brush on for a smooth top coat.

Update: Despite my best attempts, I still got bubbles. I dipped my brush in mineral spirits first and brushed slowly, with lift off at the end of the stroke. I bought an expensive brush and while this reduced the number of bubbles but I still got them (using the 2.5" sash). Interestingly my 1" detail sash brush (thinner than 2.5") did not create bubbles. So I gave up on brushes and wiped on the last two coats, using a mixture of 2/3 poly, 1/3 thinner (I went as high as 3/4 poly and while it worked ok, I found it a tad to thick). Using a fine wiping cloth, this goes on smoother and faster than brushing and no brush marks and very minimal bubbles. The bubbles that do form are super tiny, so not a concern. I found as long as you keep the cloth moving slowly with firm pressure, it does not bubble, but corners and ends are difficult and some bubbles formed there. I'm pleased with the the final coat as it is very smooth. I sanded with 200 between coats and 600 before the final coat.

Going forward I'll only use the wiping method when applying poly, although a small brush may be needed for smaller areas where a cloth is hard to control. I used a new yogurt pint container for each coat and discarded. I would not leave poly in a plastic for any extended time since I expect it will react and slowly dissolve. A metal container is better.

Tips

Use a scotchbrite pad with the citristrip to pull stain out of the wood grain.

Get a pack of shop rags to wipe up the excess citristrip. It's messy

Make sure to remove excess stain from the corners.

Wood is inherently variable and stain will appear darker/lighter and potential unevenly across variations. My stairs have two maple posts. Unfortunately they use a thin veneer for the post and it was not of the best quality for one of the posts. Specifically it did not take the stain consistently despite proper prep and application.

Don't let the stain dry when applying! This was the epic mistake that the contractor made. Old Masters says not to leave the stain on for more than 15 minutes, but drying depends on temperature and humidity so it could dry faster if hot and dry. If it dries, don't sweat yet. Wipe as much off as possible then use mineral spirits on a rag and it should come off easily. However if you let it dry (10 hours or more) then you're back to square one with the stripper. As it would seem, the wood will absorb more stain the longer it sits on the wood. For stair treads it might seem tempting to apply the stain on each tread as you move down, then wipe on the way up. However you'll end up with lots of problems; even if the stain does not dry, it will have absorbed the most on the top step and the least on the bottom step so your treads will be darkest on top and gradually get lighter. This is exactly what happened to my stairs as the contractor rushed the job. I applied stain to three treads at a time and used multiple timers to keep track of absorption time. As soon as five minutes were up I started wiping.

For larger pieces where it may take longer than 15 minutes to apply the stain, work in sections. You won't get overlap lines, at least I didn't. Again, mineral spirits is your friend here if you see any areas start to dry.


Mistakes:

Don't put plastic or anything on stained items until cured. I had been putting plastic over the stairs to keep them clean from foot traffic. I made the mistake of applying stain on the treads too late in the day. The can says it needs a full 10 hours to dry. It was getting close to 5pm, when people start arriving, so I put on the plastic. The treads were still somewhat tacky at this point. The next day I noticed the plastic has bonded to the stairs. The stain solvent must have reacted with the plastic. I was going nuts at this point. Wiping with mineral spirits did not remove it. I had to resort to a scotchbrite pad (the kind that warns it will scratch things) soaked with mineral spirits. This removed the plastic but also removed some stain too, ugh. After it dried I wiped on some more stain and it everything seemed to be ok again, whew. I also used the scotchbrite on the post which was super dumb but I wanted to lighten up bit. This was before I realized it was removing the stain, so I had to reapply on the post too.

Stir the stain with a stick. At first I was shaking the stain can to mix. This is not sufficient as some of the heavy pigments sit on the bottom of the can. You must use a stirring stick and fully mix to get a consistent color.

Always clean stair treads with a wood floor cleaner before applying another coat if anything has walked on them. Wiping the stairs with mineral spirits will remove dust but it is not a cleaner so any stains/dirt not cleaned will get trapped under the poly. You need to wait at least 12 hours or so before applying a cleaner or sanding; this time should be on the label.

Wood conditioner was not really necessary for the maple. The first coat of stain after the conditioner didn't soak in at all. When I wiped the stain off, it removed all of the color, leaving an oily appearance.

And finally the before and after. Was it worth it? My wife will say no but it really irked me so for my own sanity, it was.

Here's what the contractors did. Notice the dark section in the middle of the post.



And now



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