BLO under varnish question

Re: BLO under varnish question

Bill Tindall, E.Tn.

there is no need to sand varnish unless it is lumpy, which the first coat usually is. If the oil is lumpy steel wood it.

Re: BLO under varnish question

paul in AZ

I don't sand BLO.

Maybe a light wipe with 0000 steel wool if the surface is less than smooth.

Re: BLO under varnish question

Joe in a Cleveland suburb

"there is no need to sand varnish unless it is lumpy"

I've always read to sand between coats for the mechanical bond benefit.

Re: BLO under varnish question

Joe in a Cleveland suburb

"Maybe a light wipe with 0000 steel wool"

Thanks. That's exactly what I did. I hit the whole thing lightly with 0000 steel wool so that it felt really smooth. Then started with the varnish.

Re: BLO under varnish question

Joe in a Cleveland suburb

I went ahead and gave all the pieces to this tv stand thingy a once over with steel wool to smooth out the blo. Vacuumed, tack clothed, then started applying P&L #38.

This is my 1st time using this varnish. P&L #38 is very light in color - which is what it states on the can. That's why I put a coat of blo down first which darkened the cherry a bit. Putting down a coat of blo is what I usually do anyway.

The 38 was brushed on using a quality natural bristle brush I bought from Jeff Jewitt some years ago. I thought the 38 was a little thick (maybe because of my cold basement) and it wasn't flowing off of the brush very well plus, even though I was using slow strokes, a lot of bubbles were being generated. So I thinned it with mineral spirits. Maybe 20 or 30%. I don't know, just till it flowed off the brush nice.

Once thinned, it flowed off the brush much nicer and produced a lot less bubbles. After applying a coat, I tipped it off which all but eliminated the bubbles. Over night, the bubbles pretty much disappeared.

Saturday I applied the first coat. Sunday morning I sanded it with 320 and then applied the second coat. Taking a quick look this morning before leaving for work it looks pretty good with only 2 coats. The raised panels might need another coat.

The varnish did a nice job of highlighting areas I didn't sand very well on the doors... But for a tv stand built like a kitchen cabinet that will probably end up in the garbage some day, it may be good enough. This isn't intended to be a 'nice piece of furniture'...

The case

First time making a molding like this

Wish I had a pin nailer.

Doors

Alkyd varnish chemistry

Bill Tindall, E.Tn.

The Alkyd varnish molecules have several reactive sites on each molecule. Upon exposure to oxygen some of these sites react with oxygen and once reacted they go on to react some more in various ways. The most beneficial way is for one of these sites to join with a site on another molecule(cross link). Eventually most of the original varnish molecules are tied together through these reactive sites. But most of the reactive sites remain. Upon addition of a second layer of varnish the reacting process begins again. The reactions going on within the new layer will extend to the interface between old and new layers.

I have never discussed this topic with a varnish chemist but I see no reason why reacting molecules in the new layer won't react with old molecules at the interface and chemically join the layers.

It may well be that after many years the surface layer of old varnish becomes unreactive with new varnish. Or it may just become degraded and mechanically weak. Or contaminated. For these and possibly other reasons it could be necessary to remove the surface layer of old varnish to get a new layer to stick.

Urethane varnish is another animal and I don't know much about its chemistry. There may be no reactive sites left at its surface after it has thoroughly cured.

In any case, I doubt there is any chemistry reason to sand between coats if the coats are done within a matter of days. The first coat invariably produces a rough result. I always sand this coat. I rarely sand between the next two.

Tip for you

David Yoho

Nice looking molding, Joe. Looking at the pictures, it appears you attached the moldings with brads (???) and covered with putty before finishing. We've all done or do that. Even though the TV stand may be destined to be tossed one day (don't know why - it looks great) I thought I'd share a tip that will take your woodworking up a notch.

One trick I used on period-like pieces to hide the fact a molding was nailed is to predrill pilot holes in the molding pieces and attach with 3 or 4 penny finish nails. Set the heads below the wood using a number 2 or larger square head drive bit as your countersink. You want the head to sink enough to be able to just glue in a piece of same size square stock you cut from the wood you made the molding from. After sanding it will look like you used square pegs to attach your molding and they actually blend in and are less noticeable.

That's a neat trick!

no brad nailer-no problem

Bill Tindall, E.Tn.

Stuff needed- A pack of brad nails, a set of number drills and a nail set ground to the shape of the nail head. Drill a pilot hole the diameter of the thickness of the brad. Set it with the custom ground nail set. Result is the same as what is done with a nail gun.

That said I have come to love my pin nailer.

Yeah, but...

David Yoho

The point of my tip was really about not seeing those round or rectangular (brad gun applied) spots on moldings probably filled with whatever folks use. For certain furniture work it just sticks out like a sore thumb.

Re: BLO under varnish question

Sgian Dubh

I must admit that what's going through my mind is trying to see the purpose of applying boiled linseed oil to a prepared wood surface prior to applying an oil based varnish. I would normally omit the linseed oil underneath that type of varnish because most varnishes of this type already contain linseed oil. Given that, don't these varnishes tend to have the same effect on the wood as a 'pre-coat' of boiled linseed oil?

Many years ago, when I lived in the US, I did use the Pratt & Lambert 38 varnish quite a bit because I liked the fact that it seemed to confer a somewhat less dramatic darkening of the wood than other varnishes. Perhaps I'm remembering incorrectly, but that paler result is how I recall it … maybe someone will correct me?

I also can't remember if the P&L 38 contained, or still contains, linseed oil, but I'm guessing it does. If not, I suppose it's likely to contain some form of tung oil.

If I'm remembering correctly, that does bring me back to the general question of, 'Why apply an oil based varnish over boiled linseed oil?'

On the other hand, I have quite often applied other finishes over a first coat of boiled linseed oil. Pre-cat and acid-cat lacquers, and shellac are examples, and in each case the purpose of the linseed oil was to change the wood's base colour, e.g., to affect the colour of walnut, cherry, and even pale woods such as ash and maple.

Anyway, I'm interested to find out other people's take on this, because it's possible I've got it all wrong! Slainte.

Re: BLO under varnish question

paul in AZ

As you state, BLO changes the base color of woods [and also pops grain]. Add some exposure to sunshine and the changes occur over a matter of days and not months or years if not oiled. Specially in cherry. Then a protective coat.

Varnish alone may accomplish this eventually but nowhere near as well.

Re: Yeah, but...

William Duffield

But a 23 ga. headless pin nailer is almost invisible.

That said, Titebond Molding and Trim (No Run No Drip) glue and blue painter's tape doesn't take a lot more time, and is usually good enough for kitchen cabinets and other pieces you expect will be discarded or relegated to the rumpus room eventually. I hope that doesn't happen to your cabinet.

Another point of view: If you study country furniture (built in centuries past for any but the wealthiest clients), you will almost always find that the face frames and moldings were just nailed on with brads or sprigs and maybe filled with putty. In most cases, the nail holes have been disguised by centuries of bumps and dings, but they are still there if you look for them.

Re: BLO under varnish question

Don Stephan

An hour ago I wiped some P&L 38 thinned with mineral spirits on some cherry and hard maple turnings, and I agree that this varnish make a very light coating. If I wanted a slightly darker look, I could have wiped with boiled linseed oil, let dry, and then began with the P&L 38.

Re: BLO under varnish question

Sgian Dubh

Thanks for that Don. It does rather confirms how I remember the P&Ls 38 characteristics, i.e., a relatively light colour change to the wood compared to many other oil based varnishes. Slainte.

Re: BLO under varnish question

Joe in a Cleveland suburb

I don't know if I am right or wrong in doing it, but I have always applied BLO on cherry before varnish.

I just like the look. To my eyes it gives the cherry more immediate color. Not a lot, but some. Especially with this P&L #38 which is very light in color. Almost looks like regular vegetable oil...

Also, I could be very wrong about this, but because BLO yellows and darkens with age, I think it gives the cherry and aged look quicker than just varnish alone. The varnish likely has some BLO in it already I suppose, so who knows.

At any rate, I just like the look.

Thanks for ...

Joe in a Cleveland suburb

all the input from everybody.

I always appreciate what I learn here from you all.

do you have a picture of the difference

Bill Tindall, E.Tn.

cherry w/o linseed oil vs cherry pretreated with linseed oil, then varnish?

Re: do you have a picture of the difference

Joe in a Cleveland suburb

I'll try to do that tonight.

Re: BLO under varnish question

Don Stephan

Like you, Joe, I like the look of BLO on cherry. Of course, "blotching" is not for everyone but for me that is a natural characteristic of cherry to be recognized and appreciated. To my eye, P&L 38 alone does not completely replicate the effect of BLO on cherry, so I would also rub on a thin coat of BLO on a cherry piece, let cure for several days, and then top with P&L 38.

Re: do you have a picture of the difference

paul in AZ

I don't have any photos but having used BLO on cherry forever I can assure you that the difference is dramatic.

BLO alone is OK but to get the full benefit of it the piece should go out into full sunshine for at least a day. That really brings out the rich reddish color of the wood. Quicker by several years than waiting for unoiled cherry to begin to change. And FAR easier than staining cherry to wind up looking like an IKEA product.

Try it with a scrap piece partly oiled and partly not, with some blue tape across both areas. Put it outside in direct sun for 2 days and you will see.

that is not the question

Bill Tindall, E.Tn.

Nobody questions that oil on any wood changes the appearance. Traditional varnishes, like PL38, are formulated with a high percentage of oil. The question is whether a pretreat of linseed oil adds anything to the appearance if it is followed by an oil based varnish? Flexner says it doesn't. Joe is going to test the claim.

What's it like in 20 years?

Dick Coers

For some reason I imagine 20+ year old wood with a BLO finish is super dark. Probably influenced by wooden hand planes that are almost black, or pickup truck beds from our farm that had linseed oil on them to extend the life.

somehwat related experience

Bill Tindall, E.Tn.

We had oiled with vegie oil butcher block counter top work surface at our previous home. Indeed it was nearly black after several years.

Walnut gun stocks oiled with linseed oil get dark and stay dark.