I'm getting ready to work on finishing and I'm wondering what everyone uses to thin MOW spar varnish. I think on the tips site Bob Nunley talked about thinning spar with turps (30% turps, 70% varnish) when working with wraps.

How do the rest of you thin the spar? Also what are the ratios that you use for wraps & for overall rod finish? (Todd Talsma)

I use Ace brand spar thinned 50% with mineral spirits for coating wraps. It goes on like water and dries with in 24 hours for the next coat. So far no ill effects on its ability to adhere to the previous coat.

I have also used this mix with a foam brush (Frank Stetzer's method) with good results for finishing the rod sections after wrapping. I keep the thinned varnish in a screw top quart jug, the one that the mineral spirits came in, and work out of a small glass jar that head cement or Flexament comes in. I have been able to complete two entire rods with less then 1 fluid oz. of thinned varnish.

I'll be doing my next rod in a drip tube as soon as I get some other jobs in the shop knocked out. (Brad Love)

I've started using a product called Gumtine to thin my MOW. You can get it at art supply stores. Its primary use is to clean artists paint brushes but it can also be used to thin varnish. It is concentrated so you don't need to add nearly as much. I've found that the dry finish is excellent and the varnish doesn't dry out in the storage container like used to. It smells strongly of burnt orange. (Jim Harris)

I thin spar (Pratt & Lambert #61 spar) with Mineral Spirits to about 30%/70% for the first coat on wraps and in the dip tube. I use full strength for succeeding coats on the wraps (3 total) (Marty DeSapio)

What is the thinking on thinning the varnish that one uses on rods - either poly or spar. I read some do 10% while others suggest 50%. What is a good approach in this regard? (Frank Paul)

For dipping? I like Minwax thinned about 15-20% with Penetrol. For wiping? One part each of Interlux Classic Spar, Pure Tung Oil, and Pure Turps.

For wraps? I use one coat of Mike Brook's walnut varnish for clear or light colored wraps, none for darker colors. I use Interlux Classic Spar thinned about 3:1 with turps or the 211 brushing thinner from Interlux. After an initial two coats of spar, I sand and then use it near full strength for one more coat before a final dip.  (Bob Maulucci)

Found some info in the tips site - suggests 30 to 50% thinning. Is this standard for all the varnish coats? Are more thin coats better than fewer thick coats? Oh my, lots of questions. (Frank Paul)

As a general rule, more thin coats is a better idea than a few thick ones. (This applies to woodworking, painting your car, whatever.) The thin coats dry faster with less chance of runs and less chance of not waiting long enough to recoat, which often causes varnish to wrinkle. (Neil Savage)

What should I use to thin spar, turpentine? And will mineral spirits clean up the mess when I done?  (Lee Orr)

The directions on the can will not advise you to thin spar. That's because of EPA red tape. The same directions will however suggest what you can use to clean up. Whatever is suggested for cleanup is the best thinner, too. (Harry Boyd)

Is there a difference between paint thinner and mineral spirits? What would you recommend to thin Daly's SeaFin Super Spar? (Tim Pembroke)

I attended a finishing seminar at the Detroit Woodworking Show two weeks ago (the old dog is still trying to learn new tricks!) The lecturer said there is indeed a difference between thinner and mineral spirits. The thinner has the same additives as the finish product, as well as mineral spirits, whereas there are no additives in the mineral spirits. He recommended using the manufacturer's thinner. 

He was pushing HVLP spray systems, which I can't cost justify, but what he said seems to me to be correct for any application method. (Neil Savage)

I've seen a lot of references lately to using VM&P Naptha to thin spar varnish. I also know that some folks like turpentine while others seem to prefer mineral spirits. Other than the Pine Sol smell of turps what are the advantages and disadvantages of using these 3 different thinners?  (Larry Puckett)

For me, Naptha seems to blend with the varnish better and doesn't separate like other thinners do. I've had my dip tube filled for about 3 years and no scum or separation. All I ever do is add more. I also use gloss varnish so I don't have to worry about the settling of particles in the mix. When I dip, I dip at 80° varnish temp. @ about 1/2" per minute. No stopping at guides with thinning at 25%. To start with, I thin 2 quarts of varnish 25% with Naptha. Mix it all together in a bucket, fill the dip tube, pour the rest in one of the cans for later use. (Don Schneider)

VM&P Naptha and mineral spirits are petroleum distillates with different boiling points. VM&P naptha boils at 125 F while mineral spirits boils at about 175 F. Therefore naptha dries quicker.

Turpentine is a pine sap distillate comprised mostly of terpene oils. It boils at about 160 F so it dries about the same speed as mineral spirits. It is said that turpentine causes a varnish to flow better so "brush strokes" would smooth out better. It is also claimed that turpentine will chemically combine with some components of some varnishes and never fully evaporate. I don't know if the combined product becomes a hard resin or if it acts as a plasticizer. Good or Bad, I don' know. (Al Baldauski)

"It is also claimed that it binds with some vanish constituents and never fully evaporates."

The important thing then is does the smell ever go away? My wife won't even let me open it in the house. (Larry Puckett)

My rather unscientific opinion is that turps tends to slow drying time fairly noticeably. I had always considered this to be because it is a solvent rather than a drier, which is more or less what you said! (Robin Haywood)