02-23-2012 08:50 AM
First time here. I am building a workbench and have used a plan from "woodsmith shop". The top is made of 4 layers of MDF glued and screwed together. My question is , What should I use to finish the top? I was thinking I might use poly. any help is appreciated.
02-23-2012 11:07 AM
First, I wouldn't build a workbench with an exposed MDF surface for the top. MDF is easily damaged and when it gets dinged, pieces may chip off. Most benchtops using MDF use the MDF for in inner part and apply a 1/4" hardboard (masonite) top piece. The hardboard is much harder and does not chip or flake.
A film finish (lacquer, shellac, varnish, poly varnish) is not the way to finish a workbench top. A workbench is going to get dinged and film finishes will crack or craze or be otherwise damaged. Once a film finish is penetrated, it looses its effectiveness and adjacent areas begin to fail. No treatment is going to make a soft wood benchtop harder. I much favor a "in the wood finish". Here are two that lots of folks find effective.
First, is an boiled linseed oil and wax finish. Sand the surface to 180 grit. Mix paraffin or bees wax into heated boiled linseed oil. USE A DOUBLE BOILER TO HEAT THE OIL. The ratio is not critical but about 5-6 parts of boiled linseed oil in a double boiler with one part paraffin or beeswax shaved in. Take it off the stove. Thin this mixture about 50/50 with mineral spirits to make a heavy cream like liquid. Apply this mixture to the benchtop liberally and allow to set overnight. Do it again the next day and again the following day if the top continues to absorb it. After a final overnight, lightly scrape off any excess wax and buff. This finish will minimize the absorbsion of any water and you can use a damp rag to wipe up any glue excess. Dried glue will pop right off the surface. Renewal or repair is easy. Just use a scraper to remove and hardened stuff, wipe down with mineral spirits using a 3/0 steel wool pad (a non-woven green or gray abrasive pad is better), wipe off the gunk and apply another coat of mineral oil/wax mixture.
My personal preference is for an oil/varnish mixture treatment. Either use Minwax Tung Oil Finish, Minwax Antique oil or a homebrew of equal parts of boiled linseed oil, your favorite varnish or poly varnish and mineral spirits. Sand the benchtop up to 180 grit. Apply the mixture heavily and keep it wet for 15-30 minutes. Wipe off any excess completely. Let it dry overnight and the next day, apply another coat using a gray non-woven abrasive pad. Let it set and then wipe off any excess. Let this dry 48-72 hours. To prevent glue from sticking apply a coat of furniture paste wax and you're done. This treatment is somewhat more protective than the wax and mineral oil as the varnish component adds some protection from not only water both some other chemicals also. The waxing makes the surface a little more impervious to water so you can wipe up any liquid adhesive. It also allows hardened adhesive to be scraped off. Repair and renewal is easy. Just go throught the same scraping, wiping down with mineral spirits and reapplication of the BLO/varnish/mineral spirits mixture and an application of paste wax.
Both of the above treatments are quite protective but are easy to maintain and renew. They do not fail when the surface takes a ding.
02-23-2012 11:09 AM - edited 02-23-2012 11:10 AM
You don't want to build a film on the surface. That just makes the top slick and difficult to secure a work piece. MDF will just soak up a coat of poly, not building a film. That would work fine if you already own it. Oil varnish treatments would work well too. I'd add a replaceable sheet of Masonite--hardbboard for a work surface.
02-23-2012 11:49 AM
Welcome to the forums Larry, and as the others have suggested, you may be better served by finishing your top off with what amounts to a sacrificial surface of hardboard. If you get the tempered variety, it really needs no finish and can be flipped when distressed for a new work surface.
I'd also like to invite you to browse the video section. WOOD Online has a very respectable library of free videos for your education and enjoyment in the pursuit of learning more about the craft of woodworking.
There are two channels you can look at for specific subjects:
The first is WOODCuts.
This is the site to go for “house” videos that WOOD magazine has produced for its site visitors. Although these may have commercials in them, and thus have a bit of a loading wait, they are still solid blocks of good to know information professionally shot and edited, with clear and concise demonstrations.
The second resource for videos is WOODTube.
These are user submitted videos usually shot by woodworkers who wish to visually share tips, tricks, and techniques they feel are worth passing on. This site has a search engine so you can get more specific in your need to know area.
Don't ask advice on federal firearms law from people on the internet unless you like jail food.
- Beachside Hank, WOOD Online Video Host
02-23-2012 12:08 PM
I have an assembly table made from MDF, and used the beeswax/linseed formula Howard described, only my solvent was turpentine. This has been one fantastic finish for my use. Glue just pops off, no film to fail, and easily renewable. One caution, the turpentine makes your shop stink for several days....the MS would be much more friendly to your olfactory nerves.