Another finishing question re: poly

[TominZebulon]

I started a new thread because it is a different type of question. This question is in ref to poly. I built several of those pyrex glass dish holders from a recent Wood article as Christmas presents this year. In the same issue, it talked about why poly is good for items that may be exposed to high heat. I have never really worked with poly and thought I would follow the advice in the magazine. I bought some of that Minwax spray poly and sprayed a light coat on several of them. It came out nice, but since I am doing 9 of them, it would cost me a small fortune to continue that route. So my questions are:

1. Will it be ok to brush some poly over the first coat that was sprayed on with an aerosol can?

2. And if so, should I thin it and how much should I thin? I was thinking maybe 10-15% if I needed it.

3. Will it be ok to apply it with a foam applicator? The reason I ask is I was looking for a small natural bristle brush at the borg and the smallest I could find was 1 1/2".

Thanks to everyone for your help and understanding as I try to learn this finishing stuff! I feel my skills as a woodworker have increased tremendously, but my knowledge of finishing is just above that of an amoeba!

 

[Gofor]

The spray poly is the same as the brush-on, just thinned much more and in an aerosol can (for which you pay a premium for the convenience). My experience with the minwax brush poly is that it has a bad tendency to pull bubbles in it, even with a good bristle brush. I have had trouble with the foam applicators starting to dissolve after just a short time.
I would try thinning the brush poly about 50/50 and wiping it on with a pad made from an old T-shirt.
I am still a novice at fine wood refinishing, tho, and it is quite a bit different than spraying metal or painting houses and boats, so I would advise waiting for more expert help.:lol:

Go

 

[DaveO]

I started a new thread because it is a different type of question. This question is in ref to poly. I built several of those pyrex glass dish holders from a recent Wood article as Christmas presents this year. In the same issue, it talked about why poly is good for items that may be exposed to high heat. I have never really worked with poly and thought I would follow the advice in the magazine. I bought some of that Minwax spray poly and sprayed a light coat on several of them. It came out nice, but since I am doing 9 of them, it would cost me a small fortune to continue that route. So my questions are:

1. Will it be ok to brush some poly over the first coat that was sprayed on with an aerosol can? Yes, it will be just fine. You might consider a light sanding to give the first coat some teeth for the next coat to anchor to.

2. And if so, should I thin it and how much should I thin? I was thinking maybe 10-15% if I needed it. Thinning it will help it to flow out easier and apply smoother, but it will take more coats to get a good build. I start off at around 25% because it is easy to measure a 4:1 ratio, if I am not getting the results I like then I add a little more MS

3. Will it be ok to apply it with a foam applicator? The reason I ask is I was looking for a small natural bristle brush at the borg and the smallest I could find was 1 1/2". I have used foam applicators before with good results. Be careful of bubbles and having too much finish in the "brush" they soak it up like a sponge. Don't get the cheap kind with the wood handles, the ones with the plastic handle and stiffner will hold up much better

Thanks to everyone for your help and understanding as I try to learn this finishing stuff! I feel my skills as a woodworker have increased tremendously, but my knowledge of finishing is just above that of an amoeba!

Everyone has to learn how to do something at sometime. You aren't born knowing everything. Don't repeat that to my wife, I am trying to convince her I was :lol: :lol: :lol: It's not working very well

Good luck and show us how they come out. I can't picture what you're making :5dunce:
Dave

 

[sawman]

Tom,
I agree with Go and Dave on the thinning and I have found out that using a clear plastic beverage cup, which is disposable, is very useful. I transfer the desired amount, trial and error, to the cup and start thinning the finish to the desired viscosity and apply the finish, a small amount covers alot. As to the method of application, I have used the wipe on poly for small projects and have been very satisfied with the finished porduct. I did my shop cabinets, at least the doors, with poly using a brush, thinned some, and it turned out nice. I have used foam brushes for poly and varnish and they work well. Dave mentioned wood handled brushes as to not meeting his standards and I agree to some extent. I have found a wood handle foam brush made by JEN MFG, made in USA, that I have used for applying varnish and have had excellent results. Most of the foam brushes are not good for applying shellac or lacquer, which tends to melt them. There have been several articles in FWW on different finsihing methods which I have tried and liked. As to books I have learned from, Understanding Wood Finishing, by Bob Flexnor, Reader Digest publishing, my first book and the LOML gave me Hand-Applied Finishes, by Jeff Jewit, Taunton Press, both are excellent. It just takes time and alot of sanding to remove errors and time and more sanding until you learn how to apply finish. Have a good time .

Albert, Al or whatever

 

[woodguy1975]

I'm going to leave this one alone. :rolf:

You've got some good responses with how to deal with poly. When in doubt thin to decrease your solids and potential problems. It will take more coats, but willl apply easier.

Good Luck,

John

 

[dancam]

Thinning is the key to getting good results w/poly. Another trick is to gently heat the moderatly thinned poly. Just put the closed can in a pan of hot water for a few minutes (no open flame) and then gently stir the poly. The warm poly will flo easier and lesen the chance of bubbles.

Good luck

 

[TominZebulon]

Thanks everyone for the tips. I ended up thinning it about 25% or so and applied it with a foam applicator. I now understand what you mean, Dave, about bubbles. I had a real problem with that. But thinning it allowed it to flow real well and left virtually no brush marks. Overall, I am satisfied with the results, but not ecstatic. I probably got into too much of a hurry. I need to have these things done by Thursday evening for my wife to take to work as presents. I will see how well they look when they dry. My plan is to add another coat in the morning and maybe a fourth tomorrow evening. Hopefully that will be enough!

 

[jeff...]

I don't mean to be the bearer of bad news but... if your looking for something fast drying, it's not oil based poly. Expect about 2 weeks for poly to fully cure. I've been playing with water based polycrylic. It drys in about 2 hours and seems to be close in durablity to poly. Although I'm not sure of how it holds up to heat, please see this thread for more details.

http://www.ncwoodworker.net/forums/showthread.php?t=6059&highlight=polycrylic

Thanks

 

[Gofor]

Coating the night before is not a good option. In a pinch, you can use your oven to force cure. After 4 hours air cure, (at 70 degrees or more, to allow the flammable solvents to evaporate off) put the pieces in on top of a tray on the highest rack setting (furthest from the heat element), and set the oven at its lowest temp (hopefully not much more than 150, less if able) for about 3 hours. Do not use the "pre-heat" setting as this usually fires up the broiler element (top) as well. After the force cure, let them cool to room temp before handling. Ideally, you'd want about 125 degrees. If the oven's not an option, the heat from a halogen light or a heat lamp will also work. Making a tent out of a non-flammable (ie aluminum foil) and sticking a 100 watt bulb under it can also be used for a makeshift oven, but you'll need to throw a thermometer in it to get an idea of the temp. Letting it heat up gradually as opposed to throwing it directly into the heat is better. Altho it will stink up the house, putting them close to the heat vents or in front of the fireplace will help.
Full cure is a long time after "handling" cure. If its dry enough to sand, its dry enough to handle and take to the office party. It would be best for them not to directly contact something like plastic. etc. as it can mar the surface for the first 24 hours or so. If they feel dry to touch and not soft, wrap them in regular wrapping paper or kraft paper as opposed to plastic bags, etc.
For most organic coatings, you can use the "rule of 15". In essence, most cure times (cure before recoat, cure for handling, full cure, etc) are calculated at 70 degrees and 50% humidity. For every 15 degrees rise in temp, the cure time is cut approximately in half. Coating thickness (thicker slows cure), humidity [for catalyzed poly its faster with higher humidity, but for the varnish type (minwax) its slower] have an effect. As with all things, there is a limit for this 'rule". Over 105 degrees it doesn't appreciably shorten the cure but can add more hardness.

Not trying to push you into anything, but it sounds like you have a tight schedule.

HTHs

Go