Sealing Bora Centipede top.....??

[Crow Horse]

I just pulled the trigger on a Centipede 2' x 4' and the table top (MDF). I want to seal the top and have been searching for oil based polyurethanes (exterior) but haven't found one that says it's ok to thin. Any recommendations? Thanks in advance......

 

[alinc100]

I would use Waterlox Original. It's a thin wiping varnish. Many, many furniture makers like it, its a very common coating for hardwood gym floors. Another thought for sealing would be a primer sealer like Zinnzer or Kilz if you didn't mind making your mdf white. Oil based polyurethanes can be thinned with mineral spirits ,turpentine or naptha. Several suggest 3 poly to 1 thinner, others are 50/50 for thinning ,wicking, applications. If you go the Waterlox route a can of Bloxygen(inert gas heavier than air) prevents/slows the unused Waterlox to not film over in the can after storage.

 

[dnschmidt]

I use automotive clear coat on MDF. Now that is an option not available to those that don't have a spray booth or spray equipment but it's certainly the best option. Enough of coats, typically three, and you've completely sealed the top, bottom and sides and unless you let it set outside in a rain storm it will last forever. I paint all of my MDF jigs this way and it's proven to be the way to go.

 

[T45]

The bora has a gazillion (dog) holes in it doesn't it?
Does that need any special consideration...

 

[tarbellb]

Waterlox is Tung oil based

You could easily thin some tung oil with mineral spirits (or naphtha / turpentine) 1:1 up to 3:1

 

[Crow Horse]

I'm going with shellac to seal it because of it's quick drying time. Should I brush, pad, or rag it to apply it?

 

[rlitman]

I'm going with shellac to seal it because of it's quick drying time. Should I brush, pad, or rag it to apply it?

You'll get less brush marks by padding shellac. But shellac isn't a great workbench finish. It dries fast, and sticks to everything, but that sticking to everything makes it stick great to glue and anything else, and it's damaged by water and solvents.

I'd suggest using shellac as a "hardener". It's great as a first coat to soak in and keep the grain from being raised by a water based finish. Then top coat with a water based urethane if you want a clear finish that holds up.

 

[RTM]

You'll get less brush marks by padding shellac. But shellac isn't a great workbench finish. It dries fast, and sticks to everything, but that sticking to everything makes it stick great to glue and anything else, and it's damaged by water and solvents.

I'd suggest using shellac as a "hardener". It's great as a first coat to soak in and keep the grain from being raised by a water based finish. Then top coat with a water based urethane if you want a clear finish that holds up.

I agree with both of these points. Shellac pads on great, and its ability to stick to everything makes it a great first coat under almost anything. I did a couple of tables in multiple coats of shellac, only to have one ruined by fingernail polish remover and a college student daughter.