Replies

1. 
   jgaiennie | Jan 31, 2003 01:58am | #1

   Mark,

   There are finishing experts galore here.  I'm not one, but I use alkyd varnish.  I just think it looks better than poly and I'm a product of my dear old dad who long ago told me "never put anything on a table except alkyd varnish".  This is one of those engrained paradigms that I have trouble getting past - lol.  I apply it over a sanding sealer that is specifically formulated for use under an alkyd top coat.

   Try Benjamin Moore & Sherwin Williams, Pittsburg Paints, Devoe, Pratt and Lambert, etc. stores.  My last purchase was a Benjamin Moore flat.  What good looking stuff.

   jdg

2. 
   HowardAcheson | Jan 31, 2003 01:58am | #2

   Mark, polyurethane additive to a varnish does not make it yellow. Polyurethane is a clear resin. In most cases, interior polyurethane is made with alkyd resin with a poly additive and then an oil. The oil used has an effect on the coating color. Because poly varnishes perform fairly poorly outdoors, exterior poly varnishes are frequently made with phenolic resin which is very yellow. In addition, gobs of UV inhibitors are added to protect the finish and UV inhibitors are also yellow.

   The addition of a poly additive to varnish makes it somewhat more scratch and heat resistant. Good marketing has convince most of the new finishers that it is a superior product. For some applications it is.

   McCloskey, Pratt & Lambert, Behlan, and some others still, make plain ole alkyd vanrishes. You have to either get them mail order or find a real paint store that carries them.

1. 
   MarkMortensen | Jan 31, 2003 03:20am | #4

   I know Phenolic resin varnishes will yellow tremendously over the years, regardless of the UV inhibitors.  Is this because of the resin or the oil used with the Phenolic resin?  I've always heard/thought it was because of the resin.

   Also, I thought I'd heard that adding the urathane resin (making polyurethane) to a regular alkyd resin varnish makes it yellow more.  So a polyurethane and a alkyd resin varnish will yellow according to the oil used, resins don't make a whit of difference?

   Can you help me "grade" oils for their yellowing characteristics?  I know that Tung Oil yellows less than Linseed Oil, but I have no idea about the newer vegetable oils, cottonseed, soybean, etc.  Are they worse/better for yellowing than Tung Oil?  Then the natural question is how can one tell what oil is used in what product?  That I suppose will remain a "secret formula."

   -Mark

1. 
   HowardAcheson | Jan 31, 2003 07:53pm | #7

   Mark, I'm not an expert but a long time user of varnishes from my days as working in a boatyard and then making items for a high end custom yacht builder.

   If you want a varnish that will exhibit low initial yellowing and good "rubout" properties, an alkyd resin, vegetable oil "short oil" product is what you want. The higher percentage of resin to oil makes for a harder finish that is easier to get a consistent scratch pattern on and then to polish to a high gloss. Exterior varnish are generally made with a higher percentage of oil. Today most oils used in consumer grade exterior varnishes (when you can find them) are linseed oil or vegetable oils and alkyd resin with some UV inhibitors. The higher percentage of oil makes the varnish more flexible so it can deal with the changing environmental conditions in which it is used. It also is a good choice for coating a soft wood that is easily dinged and dented as it is flexible enough to give rather than to crack. But, its softness makes it less easy to rub and almost impossible to polish to a high gloss.

   Spar varnish (real marine coatings, not the junk in the big boxes) are made with phenolic resins and heavy amounts of linseed oil (the better ones use some or all tung oil) and contains lots of UV inhibitors. They are very soft and they are very yellow by design to deal with the sun.

   Polyurethane can be an additive to any of the above finishes. It's intent is to make the resulting product more scratch and heat resistant. As I said before polyurethane is a clear resin. However, adding polyurethane to a varnish will reduce its adhesion and causes the finish to deteriorate faster in the sun. Therefore exterior poly varnishes and spar poly varnishes contain very high concentrations of UV inhibitors to protect the finish from the sun. This makes poly containing varnishes more yellow. Any varnish containing polyurethane is much less satisfactory for "rubbing out" as the polyurethane resists consistent scratching. After all, that's the reason the poly was added to the finish. In other words, poly will never look clearer or glossier than it does right out of the can.

   All lacquers and varnishes contain "plastics". When varnish containing poly is applied heavily or in multiple heavy coats, it can look somewhat "blue" which cause many to think that it is "plastic" but standard varnish and poly varnish applied to the same film thickness will probably be indistinguishable from each other.

   As to oils, the lightest is generally the vegetable, flax, etc oils, followed by tung oil and then linseed oil. It is the darkening of the oils over time that changes the long term color of varnish as far as I know.

   Edited 2/1/2003 1:50:44 PM ET by Howie

1. 
   MarkMortensen | Feb 01, 2003 08:21am | #8

   Thanks everyone for your comments.  I've read quite a bit about finishes, but have little practical experience so I'm really still a newbie in training.  I probably know enough just to be dangerous!

   At least now I have a clearer understanding of what poly resin is and its effect on varnish.  I'm going to check some of the online links that were mentioned and buy at least one can of a simple alkyd resin varnish.  I guess with experimenting one keeps learning and I'd like to 'feel' and 'see' for myself the difference in 'plain varnish' compared to one with poly added.

   Thanks again!

   -Mark

3. 
   jonsherryl | Jan 31, 2003 02:56am | #3

   Mark, I'm with you on this one. I don't like the polyurethanes. They are too hard to rub out. Unfortunately, the public has been sold on their greater durability...and also on the new "environmentally friendly" water based acrylics...I wonder what hidden toxins reside in those?...but I'm sure we'll discover all that in a decade or two.

   Until recently, I was able to get a private label "ACE" brand alkyd varnish, but I think now even they've succumbed to modern wisdom...So, like you, I'm on the hunt for a new source.

4. 
   RW | Jan 31, 2003 06:47am | #5

   I can comment on where to get and characteristics. Behlens is the one I see most often. Woodcraft, Garret Wade (I believe) and Homestead (http://www.homesteadfinishing.com) all carry RockHard Table Top varnish.

   Characteristics? If you get used to poly, which, as much as I dislike it, is a breeze to brush, RockHard will take some patience. It's very thick in the can. It brushes much better when cut, but after trying various solvents, mineral spirits and naptha both make me less than thrilled. I've heard a lot of commentary on what else to try, but it's all counter-intuitive thus far. If Behlen sells (and they probably do) a reducer specific to that product, I'd probably buy it now. China bristle or better is pretty much required. The skin forms quickly, but the surface doesn't tack for at least 8 hrs in average conditions. In a cold basement, you might still leave fingerprints the next morning.

   When it's dry, it's very crisp - by that I mean visibly glossy, looks hard. It does, from the start, impart a slight amber to the piece. When it's fully cured (I tend to give it a few weeks) it rubs out very well. But 48 hours after application, even sanding it doesn't work so well. Like any varnish, you should scuff sand between coats. Spirits is a decent lubricant here. If you use parrafin oil, you're running unnecessary risks with adhesion.

   I've established a love hate with RockHard. I love the end result. I dislike the effort it seems to take me to get there. Patience is the key, and when I lose it, leaving the piece sit for another 24 hours before grabbing a brush works wonders. Best of luck.

   " Clothes make the man. Naked people have litte or no influence in society" - Mark Twain

5. 
   Gretchen | Jan 31, 2003 03:17pm | #6

   You need to go to a real paint store not hardware (probably) nor big box.  Home Depot stopped carrying non-poly varnish about 3 years ago.

   Gretchen