Spar Urethane, bumpy table top

I used Helmsman Spar Urethane spray on a computer desk table top and although it has been 24 hours it still feels tacky, but my big concern is that it feels bumpy. The humidity level here in Arizona is 68% so the tacky doesn't worry me as much as the bumpy thing.
I sanded the table top down reaeeealy smooth, and stained it. It was nice and dry and smooth before I applied this stuff.
Question:
Did the Home Depot man sell me the wrong stuff? Is this stuff any good for desk tops? I wanted something really smooth. Am I supposed to sand this down? This was a spray can and I think I'm feeling the small particles that sprayed out onto the surface. I followed the instructions.
Is my table top screwed? Should I sand it down and put something else on it?
I'm not a furniture builder, I'm a desperate software programmer who couldn't find a certain type of computer desk after 2 weeks of searching funiture shops... I about have this thing finished and it looks really nice but this surface don't look right.
Richard
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Well, Spar Urethane is made to be flexible. Spar, as it a part of a sailboat or ship's rigging. And the UV filters probably aren't going to be all that necessary for a computer desk, even in Arizona, although I could be wrong on that. So, yes, the man in the orange apron steered you a bit off course. A spray lacquer might have been a better choice. Say, a Deft product, or something similar. Helmsman is good for front doors and outdoor furniture, where the wood has to deal with moisture and sunlight. And there still are likely better products for that use.
What you used for a stain could have an influence on what the spray varnish is doing. As could the humidity, and the temperature. The best advice, from a finishing standpoint is to be patient. Unfortunately, it may be another two weeks until this cures hard enough to be a desktop surface, and then, maybe not.
Are you in a huge hurry? The best writing surface I have ever had on a desk was plate glass, custom cut and polished to size. Once the stuff starts to not be tacky, you can put the glass on it, and go back to writing code.
Good luck.
Patriarch
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Thanks. The glass idea might work but I really wanted a wood top... I don't do any writing, just typing. I don't chop meat on it or anything like that... just wish this would have turned out better.
Richard
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And you can still have it. If the urethane does not work out, sand it smooth and put on a couple of coats of shellac. The nice thing about shellac is that it adheres to just about anything. Just keep your dripping soda cans off of it.
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look at the instructions, After it dries sand it lightly with 220 or better sandpaper and reapply then sand again then reapply and so forth until the desired look.
Len

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I suspect you are getting large drops that are not thoroughly mixed.
See if they have the same varnish in a can and try brushing instead of spraying your last two coats. Make sure you use a good nylon or poly brush, preferably tapered. I like a 2 1/2" sash brush.
Rich wrote:

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When using a can which I occasionaly do, I always put the can in warm water before starting. This thins out the spray and atomizes the spray better. Wipe the can well. What I am assuming that is happening is that you are getting a little spitting, the warming of the can prevents that from occurring. Follow the directions that DIYGUY gave you they were very accurate... But try the warming of the can... Yea I know you live in AZ, but the nights and mornings are cold, and your home is probably air conditioned... So the can might be cold.
Rich wrote:

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Urethane is not my favorite finish because it can be tricky sometimes, and it is a bear to remove, but don't panic yet because chances are what you are feeling is buildup where you stayed too long in one place with the spray. This can be evened out by going over the dry finish with a block wrapped with sandpaper. Take your time and don't be nervous when seeing "white spots" appearing as this is normal. And don't be overly aggressive with the sandpaper or you will cut right through the finish. You probably want no lower than 220 grit or so. After you have leveled the surface you can then go over it with extra fine steel wool (000). When you have done your best to even out the surface and your fingers tell you it is no longer bumpy you can clean up the dust with a tack cloth made from the same urethane. Just spray a clean, fine cotton cloth with a pass or too and fold it in half. Let is sit for a bit. When the cloth feels mildly sticky to your fingers drag it over the surface. This will remove any residual debris. Next clean the surface with denatured alcohol in another cotton rag. Don't go overboard here, less alcohol is better (both for you and your top!)
Now you are ready to continue finishing your top. I like brushing but to each his own. Make your spray passes very, very light and thin. Plan on having to do the above steps again and again - likely three more times. After each coat be sure the surface is completely dry before going over it. For the last coat use just steel wool (0000) wetted with alcohol. With each pass of the spray you should be gaining in confidence about how much to lay down but always remember to err on the "less is more" side of the equation.
Good luck ..
Rich wrote:

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I've used spray poly on a bunch of projects and the first coat seems to take several days to dry completely. The second and third coats dry in a more reasonable period of time it seems.
As for the roughness, that's pretty normal. You need to take fine (220 grit) sandpaper and go gently over it. Apply a second coat, allow to dry and then sand it again. Apply a third coat and you should be done. A dust free environment is of utmost importance here. After sanding be sure to thoroughly clean off the project before applying another coat. Try to keep the area as dust free as humanly possible.
--
Jeff P.

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Jeff P. wrote:

After sanding I wait overnight for all the dust to settle, wipe off dust as suggested in other posts, wait an hour or so, wipe off dust again, and then varnish or finish. Small things can be placed under a canopy of dish cloths or sheet of plastic but for the large things - I give dust time to settle.
Josie
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