Replies

1. 
   SteveSchoene | Nov 12, 2010 11:24am | #1

   I suppose it must have some UV blockers, but one drop is apparently sufficient to be able to put that on the label.  Minwax Helmsman has faired very poorly in comparison tests so the amount must be minimal.  And, while UV absorbers might have some retarding effect on color change in cherry, it does breakdown over time sos the effect is temporary.  Cherry will darken.  If that's not what you want then use a different wood.  (Red birch or alder make good cherry substitues, for example.) 

   In any event, using spar varnish, even the good ones whose UV protection is much greater, isn't a good idea for interior furniture because spar varnish is too soft.  That's because it must be flexible for exterior use where there is a wide range of humidities and where many of the objects to be varnished, such as boat parts are also flexible.  For furniture, interior varnishes are superior products and provide greater protection from water damage than exterior varnishes.  They are harder, and can much more easily be rubbed to to any desired sheen. 

   By the way, it won't be necessary to strip one coat of the "tooth" for the other varnish.  If your goal is for the cherry to stay as light as possible, then use a non-poly varnish alkyd based around soya oil, such as Pratt & Lambert 38. 

2. 
   HowardAcheson | Nov 12, 2010 11:25am | #2

   Why did you use that product?  It's intended for exterior use and is less durable and water resistant than an interior rated product.  Exterior finishes are made to be soft and flexible so they remain adhered as the wood expands and contracts.  The manufacturer adds oils to create the additional flexibility.  The additional oil reduces the water and moisture resistance of the finish.

   The is very little UV inhibitor in Minwax Helmsman.  True marine finishes are not made with urethane or poly.  Urethanes are quickly damaged by the UV from sunlight causing the finsh to become dull and more amber until it begins to crack and peel. 

   There is so little UV inhibitor in Helmsman that it will probably have no affect on the darking of the cherry.

   I would suggest you apply your subsecquent coats using an interior rated finish.  It will produce a harder more durable finish.  Let the Helmsman cure for at least 6-7 days, scuff sand it with 320 paper in a flat sanding block sanding in the direction of the grain.  Then vacuum and apply 2 (better 3) coats of interior clear.

3. 
   econ_guy | Nov 12, 2010 01:20pm | #3

   Thanks for the helpful comments.  I am not a very experienced wood finisher and I'd read about others using spar varnish, so I thought I'd give it a try.  Anyway, I've already finished the piece using PL 38, as you suggest.  It looks great, so I am not worried.

   Thanks again.