Sealing wooden doors

[sploo]

A slightly off topic (but still wood related) question...

I've bought a set of paneled pine doors for my house (all going to be used internally). The finishing instructions tell me that I can paint or stain them, but that they're not suitable for polishing, varnishing, waxing or treatment with teak oil.

So, what's the difference between painting and varnishing? I would've thought that both coatings would have a similar affect in terms of sealing and protecting the wood. As they're going to be used inside, UV light isn't a great issue either.

Anyone know why varnish would be a problem?

[vladdy]

latex paints and stains both take a 'set' relatively quicky, same a a thin water based wipe-off stain...
an oil based paint or varnish are slower drying, and have more tendancy to 'whisker', where very small portions of the wood will absorb the oil and slight lift or seperate from the finished portion.
a multipart finish for softer woods usually starts with an initial 'sealer' coat that dries quickly, and then fine sand to remove whiskers, and then heavier slower drying top coats followed by finish procedures depending on final result desired and glossiness of end finish.
for varnish or shellac, I usually start with a very thin sealer coat of 'linspeed' or similar fast drying linseed oil based products.
for outdoor resistant finishes I use thinned varethane types for a sealer coat, depending if it's utility purpose, general home wood, fine cabinetry, or firearm furniture, all have differing final requirements...
finally, depending on the quality of the wood, some products will absorb coatings at much different rates in different areas of the wood, creating unwanted 'shading', a thin sealer coat helps to reduce this.

..enjoy..

[sploo]

Interesting... thanks.

Does that mean I could (get away with):

1) Apply a first coat of varnish, let it dry, then lightly sand, before applying a second coat (with no sealer ever being used)?
2) Use a shellac based sanding sealer (I happen to have some in the garage) before lightly sanding, then applying a varnish?

[mlind]

Just curious what kind of wood are the doors made of? If it is a soft wood such as pine you definetely want to use some kind of sealer. If the doors are hardwood then it is discretionary.

Are you planing on staining or painting the wood? Stains make the wood darker and bring out the "character" of the wood...Character meaning the wood grain. Paint covers up the wood.

I would also suggest using a polyurethane rather than varnish as poly lasts longer and is semi-easier to apply and control rather than varnish... Don't skimp here use a hi grade polyurethane. I like Helmsman the best.

Varnish and/or polyurethane is the last step in the process.

Your choices are as follows.

Paint probably 2 coats.

Lightly sand with 150-220 grit sandpaper and wipe off dust with a lint free cloth.

OR

Lightly sand with 150-220 grit sandpaper and wipe off dust with a lint free cloth.

Apply Stain and wipe off excess stain with a lint free cloth.
Varnish or polyurethane. Usually the more coats added the better the results.

One more thing.... Before applying stain do a little spot on the underside of the door to make sure the color is what you want.... THere are many different kinds and colors of stains..

Hope this helps.

[sploo]

Thanks for the reply mlind. The doors are pine, and are pretty close to the colour I'd want (so I don't want to stain them).

I've got some clear polyurethane varnish that I've used on a pine cabinet before (with no sealer) and I was pretty happy with the results (I used a coat thinned with white spirit, let it dry, gently sanded it, then applied an unthinned coat).

I've used a shellac sanding sealer on some small hardwood boxes I've made (with wax to finish) but I've never used a sealer before applying varnish.

This evening I put a coat of the varnish on an offcut from one of the doors, and a coat of shellac sealer on another. I'll lightly sand both tomorrow and apply a varnish coat on each... then work out what to do from there.

I can't see why there should be a problem (I've never had any issues with the pine cabinet I made, and varnish coated). I'm still just trying to work out why the instructions for the doors advise against varnish .

[mlind]

Agreed.

The only time I use a sealer with pine is if I'm going to stain the wood. If just varnishing pine sealer isn't needed. I'm sure your doors will look great!

Originally Posted by sploo Thanks for the reply mlind. The doors are pine, and are pretty close to the colour I'd want (so I don't want to stain them). I've got some clear polyurethane varnish that I've used on a pine cabinet before (with no sealer) and I was pretty happy with the results (I used a coat thinned with white spirit, let it dry, gently sanded it, then applied an unthinned coat). I've used a shellac sanding sealer on some small hardwood boxes I've made (with wax to finish) but I've never used a sealer before applying varnish. This evening I put a coat of the varnish on an offcut from one of the doors, and a coat of shellac sealer on another. I'll lightly sand both tomorrow and apply a varnish coat on each... then work out what to do from there. I can't see why there should be a problem (I've never had any issues with the pine cabinet I made, and varnish coated). I'm still just trying to work out why the instructions for the doors advise against varnish .

[sploo]

The samples I varnished have both had several days to cure, and both look fine to me.

I still can't work out why there should be a problem using varnish on the doors, so I'm going to go for it! If there does turn out to be some big problem (given it's wood involved, I expect it'd show up over the next few months) I'll post an update.

Thanks to those that posted with info.

[sploo]

As promised, here's a quick update. It's now been two weeks since I used a clear satin polyurethane varnish on the doors. I've not spotted any problems, and the doors look great.

I guess I'll only know for sure once they've been through a year of dry or humid/warm or cold days, but cross fingers...

[metaldr]

One cautionary note on these types of doors. Make sure that the panels do not get painted/varnished in place. They have to be able to expand and contract as the moisture level changes. I have the same type of doors in my house with a painted finish. After going through one winter you could see where the panels contracted across their width leaving a small area showing that didn't have any paint on it. The original (100yr old) doors had panels that cracked because the many coats of paint locked them in place.

[sploo]

Hi metaldr,

Yea, that was my concern with the doors. I couldn't understand why painting was apparently OK and varnish wasn't, as the main risk I could think of (that you 'glue' the panels to the uprights) would be the same (or worse) for paint than varnish.

When I varnished, I made sure to keep the coating thin along the edges of the panels, so hopefully I won't have stopped them moving.