Help with poly on school desks!

[overland]

I've been building batches of desks for my son's school out of maple plywood. I built a batch during the summer and varnished them during hot weather. (I brushed it on.) No problems. Recently I did another batch and had all sorts of problems with the finish. It didn't level out that well--or rather it seemed that the air bubbles left a lot of little blips on the surface. I've been using Mini wax's fast drying satin poly. My questions are these:
1. What can I do to level out the surfaces I've already done?
2. What should I do to do a better job with the remaining desks. Should I use a different brand of poly? Should I thin it a little? Do I simply need to do the varnishing in a warmer space? (I think the best I probably can do for temperature is the 60s).
I'll be grateful for any advice.

[Sawdustd]

First, go to the head of the class and get a gold star. It's rare now days that a parent can make a contribution to a school which will last for years.

Bubbles and nibs? Welcome to Miniwax. To smooth the surfaces, sand lightly, by hand, with 600 grit and a block and clean up with a micro fiber cloth which collects dust like a magnet. The desks are not fine furniture so close counts. They are going to take a lot of abuse in the future. Kids are kids. If you are really concerned, after sanding, go in search of a wipe on finish for a final top coat.

Applying a poly finish in the 60's is right on the edge, IMO.
In the future, consider using Arm-R-Seal or General Finishes High performance. No bubbles and durable surface protection.

Oh, forgot to mention. How old is your Miniwax? Fresh is always better. Good luck.

Dave
.

[overland]

Thanks for the excellent advice. This problem has been tormenting me for weeks and now I know what I can do. I'll get better poly and find a warmer place to finish the remaining desks.

[overland]

Alas, more questions:
General Finishes High Performance is water based, right? Does that mean I can use it indoors without worrying about breathing the fumes? Also, if I wanted could I apply a coat over the top of my Miniwax oil based poly? Finally, how do I apply it? With a regular brush, a foam brush, or something else?

[Restorer]

There is nothing wrong with using Minwax poly oil base. The problem is you tried to use it in to cold of conditions. Especially if you were applying under 60 degrees. Sand to level an you may have to use something as rough as 220 if the problem is bad. Normally between coats I use 400 to 600 grit, but if you are really having to level and get rid of bumps 220 may be where you need to be. again the problem is not the finish but the conditions it was used in. Waterbased anything will give a different look then the oil based you started with. I don't think oil based puts off enough fumes to worry about. I finish in a back room inside many times during the winter. Heck at Christmas rush times I have projects being finished in about any room in the house. If you must go to something different Sherwin Williams fast dry varnish. It is not a poly but old style varnish, can be had in oil or wb. I have only used the oil. If you poly is putting off a bad order could be a chance it is old.

[JR1]

GF HP doesn't produce any noxious fumes, but you should still use a particulate mask when applying it. In general waterborne finishes will spray beautifully, wipe on, or use a foam brush. HP is more scratch resistant than other GF waterborne but not as chemical resistant.

In general waterborne finishes are compatible with just about anything but do a quick test to make sure. BTW you should let the finish cure for 72 hours at >60F before rubout or putting it into use. It will cure enough for recoat in <1hr.

[overland]

I don't have a spray booth. What do you suggest, wiping on or using a foam brush? I don't have experience with either.

[JR1]

Either will work just fine. It's self leveling so no problem with needing to be super precise. Just make sure that the top you are finishing is level. For larger flat surfaces the foam brush works better. Get a large and then a couple smaller. Make sure to wash them out good with water after use as if the finish sets up in them they will be stiff and worthless. One of my friends uses a foam roller for large surfaces but I've never tried it. Make sure to read and follow the instructions on the can!!

[overland]

What about vertical surfaces?

[JR1]

You can do vertical surfaces just apply a thin coat.