Covering furniture with polyurethane

[MikeMc]

Hi all,

I am new to staining and have a question. I have assembled a few pieces of shop furniture including and assembly table and some cabinets.

I am staining these pieces with Minwax natural stain after using a pre-treat. I am only staining the exterior surfaces that will be visible when the pieces are complete.

My question relates to the final polyurethane coating. I intend to do the interior of the cabinets and drawer boxes but do you recommend polyurethane over the entire pieces? Things like the underside of the assembly table and the underside of the cabinet or is it better to just seal the parts people will come into contact with?

Your experiences are appreciated.

[Gregory Paolini]

Hi all,

I am new to staining and have a question. I have assembled a few pieces of shop furniture including and assembly table and some cabinets.

I am staining these pieces with Minwax natural stain after using a pre-treat. I am only staining the exterior surfaces that will be visible when the pieces are complete.

My question relates to the final polyurethane coating. I intend to do the interior of the cabinets and drawer boxes but do you recommend polyurethane over the entire pieces? Things like the underside of the assembly table and the underside of the cabinet or is it better to just seal the parts people will come into contact with?

Your experiences are appreciated.

For shop cabinets, you sould be OK just putting poly on the surfaces that you'll come in contact, but for real furniture, you'll want to poly both sides of a board evenly - Poly seals the wood, restricting the ammount of moisture that can enter/exit the wood during seasonal humdity changes. If only one side has poly, the other can absorb more moisture, and thus expand more. And if one side of a board expands more than the other, you'll get warp/bow/cupping/etc...

Atleast, that's the jist of it...

Hope this helps,

Gregory

[bois]

I've always read that you want to treat both sides, especially for table tops to minimize the likelihood of bowing or cupping (presumably from uneven flow of moisture). However, Bob Flexner (whom I consider to be a finishing guru) has widely disputed this as a woodworking myth. Here's a good explanation from Woodshop News. I almost never finish the undersides of table tops, and even in the wild humidity changes here in New England, I've never had a problem with warping or cupping on a table top (at least after the finishing stage). I look at a lot of antiques too, and often times I'll see 100 year old pieces with unfinished undersides and dead flat tops. So I do wonder if this is a myth concocted by the finishing companies to sell more product

[went_postal]

I've always read that you want to treat both sides, especially for table tops to minimize the likelihood of bowing or cupping (presumably from uneven flow of moisture). However, Bob Flexner (whom I consider to be a finishing guru) has widely disputed this as a woodworking myth. Here's a good explanation from Woodshop News. I almost never finish the undersides of table tops, and even in the wild humidity changes here in New England, I've never had a problem with warping or cupping on a table top (at least after the finishing stage). I look at a lot of antiques too, and often times I'll see 100 year old pieces with unfinished undersides and dead flat tops. So I do wonder if this is a myth concocted by the finishing companies to sell more product

I had often wondered about that as well... I wonder how much of the "flexing" of wood is caused from poor preparation/building as opposed to not having stain/poly all over everything. Wheres it locks in the current moisture content, couldn't that be a bad thing as well? To me it seems more logical to allow the wood to continue to "breath"

NC sees it's fair share of moist air.. So far I have been VERY lucky that the stuff *I* built has not gone too far out of shape and I only stain "visible" stuff simply because I am lazy and HATE finishing. =) I am always REALLY careful about making my table tops though... Another controversial thing is alternating the crown when doing large glue-ups... I have done that for years and it has worked very well for me.

[Rick LoDico]

Is there a reason for finishing the insides, especially the drawers? It's not usually recommended. I usually finish the underside of tops but not the underside of cabinets.

[MikeMc]

Is there a reason for finishing the insides, especially the drawers? It's not usually recommended. I usually finish the underside of tops but not the underside of cabinets.

Really? It was recommended in the plans I got from an article in American Woodworker from October 2002. It says and I quote "Remove the drawers and finish the inside of the cabinets. Apply a minimum of two coats of polyurethane. Dont forget to finish the drawer boxes and runners. The polyurethane helps to make the drawers glide smoothly."

So, I was yet again going to follow instructions with no real facts backing them up. The majority of the cabinet was constructed from 3/4" and 1/2" plywood and as I understand there is not much movement of these materials even with moderate changes in humidity.

And TBH, this thing has 13 drawers so after sanding the fronts with 100 grit, 150 grit, 220 grit and again with 220 after pre-staining I am not anxious to cover the entire set of drawers in 2 coats of polyurethane. But my original plan was to do it to provide some sort of protection to the drawers as they are shop furniture.

I am glad I posted the thread as there has been some pretty good information so far.

[Rick LoDico]

I can't believe AW printed that. There won't be any wood movement but there will be a long, long lasting odor. Just sand the drawer sides.

[AceHoleInOne]

Everyone has an opinion on this, so here is mine...wood moves...anything I can do to help or slow down or minimizing it, especially solid wood construction, I do it. I have built several chest that have a keyed lock. And yes its finished on all sides and the wood still moves making the locks mechanisms tight , but would hate to see how much it moves without finish on all sides. Solid wood is like a sponge and absorbs moisture. I finish all sides, period.

-Ace-

[bois]

I would never finish the inside of a chest of drawers, it could take a year before that stops off-gassing. You don't even need to finish runners and kickers, a good coat of wax will give you all the slickness you need for a smooth drawer. Flexner's whole point is that you can't stop wood movement, you can only slightly slow it down. If you consider wood movement in your design, construction, and material selection this should never be a real issue.

[AceHoleInOne]

To work around the odor, consider shellac or water-based to seal interior surfaces. Just a thought.

-Ace-

[went_postal]

I would never finish the inside of a chest of drawers, it could take a year before that stops off-gassing. You don't even need to finish runners and kickers, a good coat of wax will give you all the slickness you need for a smooth drawer. Flexner's whole point is that you can't stop wood movement, you can only slightly slow it down. If you consider wood movement in your design, construction, and material selection this should never be a real issue.

Can't beat this stuff for runners:

http://www.leevalley.com/US/wood/page.aspx?p=32182&cat=1,110,43466

[bois]

Can't beat this stuff for runners:

http://www.leevalley.com/US/wood/page.aspx?p=32182&cat=1,110,43466

Great tip there - I'm wondering if that tape could also be layered to help dial in the exactly sized gap below the drawer?

[went_postal]

Great tip there - I'm wondering if that tape could also be layered to help dial in the exactly sized gap below the drawer?

Not sure... never tried that. They make that stuff in all different shapes and sizes. I have table saw inserts made out of the same stuff and it's great. Very low friction.

I have used it in application where the drawer was simply a box going into a hole in a carcass... none of the annoying wood on wood scraping noise and I have never had a drawer stick on me yet.

And... it will stick to finish. =)

[Munni]

Hello, I has children’s furniture that I had put in storage for several years. We recently took it out of the shed to use for my youngest, and there was a bad musty/moldy smell. We cleaned every piece twice, the second time with a vinegar and water solution. The smell still remained. So, I applied Zinsser odor eliminator and it did the trick, and it seemed to work. The rep at Home Depot recommended sealing the furniture to include the drawers to make sure so mold is no longer an issue, so I used oil based polyurethane, which I now realize is a mistake. We left all of the drawers outside for 30 days to cure in a covered patio and most of the smell is gone, but there is still a faint smell. Is it safe to put my kid’s clothes in the drawers and for him to sleep in the room?

[Mark J]

Is the polyurethane surface still tacky when you touch it?  Or has it dried hard?

If the later than I suspect you just need to give it a bit longer.

[wtnhighlander]

Agree with @MarkJ. Polyurathane is prefectly safe for contact with clothes and such, once cured. The smell can take a lot longer to dissapate than is required for the film to harden.