Preparing oak trim

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Old 11-12-05, 04:09 PM
FrankO38
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Preparing oak trim

Hello all my name is Frank and I'm a new do it yourselfer. I am doing some home improvements and am looking for some help
prepping oak for staining. I'm starting with my door casing. Correct me if i'm wrong but with new wood should it be sanded before staing and if so what grit sandpaper should be used. Also, if applying more than one coat, do you need to sand in between applications and if so what grit? Finally what sealer should I use polyurethane? or varnish? and what is the advantage or disadvantage with either of them? Thank you in advance Frank
 
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Old 11-12-05, 06:36 PM
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Welcome aboard, Frank.

New trim would benefit from a light sanding with 180 - 240 grit paper. Wipe it down with some mineral spirits on a cloth to check for surface contamination such as fingerprints as these will spoil the uniformity of the stain. I would prepare it, stain, and finish it prior to installation. Between coats of finish, 240 grit is usually enough to knock down the nibs before the next coat. I sometimes use green scotchbrite pads, unless there a runs or sags to be flattened.

Rather than a sanding sealer, many use a first coat of polyurethane thinned with mineral spirits to 50% of full strength. This thin coat dries fast and will sand easily. Be sure to allow sufficient time for thorough drying between coats. Polyurethane is a varnish.
 
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Old 11-12-05, 08:04 PM
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Not to contradict chfite, but maybe to add to his words and perhaps look at it from a different viewpoint. I would prep the trim using 120 grit sandpaper. Oak trim often has mill marks on it which look like planer marks. What happens is the shaper blades make small indentations in the wood where the wood fibers are alternately compressed/uncompressed as it passes through the shaper. Usually, the goal of sanding is to remove these mill marks so that they are removed before the wood is stained. To do this, you need to use an aggressive grit, 80 or 100 and work your way up. The time you spend sanding is well worth it, because once you put on the stain and finish, it's a little late to go back and do a better job of sanding. Personally, I never sand my trim any higher than 120 grit. The reason I don't is because if you sand with a higher grit it can close the grain of some types of wood and they will not accept stain as readily. I've found that sanding with 120 grit works well for me, especially since after the wood is stained, I use sanding sealer, which raises wood fibers so that they can be sanded off (using 220 grit).

You do not need to sand between coats of stain, but you do sand after the wood has been sealed (usually just after the first coat). After your last coat of finish, the wood is usually smooth, unless some particulates have gotten into your finish. They can usually be taken out after the trim is cut and installed by rubbing the trim with #0000 steel wool.

Regarding the type of finish you use, "varnish" is not exactly the same as polyurethane, they are very different types of finishes, even though polyurethane might be classified as a type of oil-based varnish they have different characteristics. Varnish is not as hard as poly, many varnishes will yellow with age, and varnishes are easier to sand, thus easier to scuff. Varnish generally dries faster than poly. Poly is a very hard finish, which is one reason it is used on floors. When poly dries to the touch it is still not really dry, because it continues to form bonds at the molecular level, which is what makes it such a resilient finish. Poly is also quite clear and generally will not yellow. If this is not desirable, it can be tinted to give the finish a certain glow, whether it be a red hue, or golden, etc. Polyurethane is also available in either oil based or latex product lines. The drying time of oil based polyurethane is a little longer than most varnishes, but that usually is not a huge factor. I opt to use polyurethane in almost all of my trim preparations because it costs virtually the same price and is a much harder, more durable finish that will hold up to the occasional nick and scratch, can of soda that leaves a ring when you pick it up, or the plant that someone accidentally gave too much water and didn't wipe up right away.
 
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Old 11-12-05, 08:14 PM
FrankO38
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Thank You

Thank you guys for all the advice. That was my first post on this board and I thank you for a speedy reply. I plan on logging on here for more help in the future. Thank you again Frank
 
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Old 11-13-05, 09:48 AM
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I would like to add that when ever you sand wood to be stained, you should always sand with the direction of the grain. Sanding cross grain will often result in scratches visibles once the stain or varnish is applied.
 
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