I am by no means a varnishing expert.  I followed the advice on the CLC web site like you and I am happy with the results, even with my many runs (they seem to disappear as you use the boat, or maybe become less noticeable as it get's scratched and dirty).  I cleaned up the surface with a clean rag soaked with denatured alcohol after sanding.     

   Thanks! 

I'm a little concerned, though - denatured alcohol between varnish coats?  or just first clean-up of sanded epoxy?  I know it's safe on epoxybut I have the notion that it will damage the polyurethane.

   I just wiped down between varnish coats with water, then a tack cloth-- which I'm sure is advice i picked up from this forum somewhere.  But as someone who once accidentally thinned varnish with denatured alcohol rather than thinner-- and then applied that varnish, I can assure you denatured alcohol will have no ill effects.

Just to be clear, tack cloth on epoxy or varnish before varnish (or paint) is OK.

Tack cloth on epoxy before more epoxy is to be avoided.

Too, let's be clear there's two different kinds of varnish: traditional oil-based and the newer polyurethanes, which can be either oil-based or waterbased. What you use to clean up (mineral spirits vs. plain water) is how you tell the difference... besides the smell.

Denatured alcohol shouldn't affect oil-based varnishes once they're fully cured but will affect water-based polyurethane varnishes whether cured or not so tread carefully here.

The oil-based are best for marine use. The water-based generally don't give the same UV protection but there are exceptions for a few products as some from Hydrocote.

(That alcohol-thinned varnish you went ahead and applied ended up giving you a staisfactory finish once it'd dried? That's pretty amazing!! 

"I'm a little concerned, though - denatured alcohol between varnish coats?  or just first clean-up of sanded epoxy?  I know it's safe on epoxybut I have the notion that it will damage the polyurethane."

Yes, that is what I did.  Dampen a clean rag with the alcohol and wipe the sanded surface.  The varnish has typically cured for atleast 24 hrs between coats, manytimes  even longer.  I used the Interlux Schooner varnish.  It looks good.   

   Thanks, that's pretty clear now!  Especially in light of spclark advice that denatured alcohol is safe on oil base varnish, which is what we're on about here.  Tack cloth seems like an easy way to go.

   I put the following together for a friend who was finishing up their epoxy work on their kayak...

I thought I would try to summarize my recommendations in a sequential manner, starting from where you are in the building process...

1. Clean up the existing rough ares, the sand the entire boat - 80 grit, then probably 100-120 grit
2. Using the West System rollers, re-apply another VERY thin Epoxy layer.  You will probably find it very helpful to “tip” that epoxy layer with the foam brushes
3. Once cured, re-sand - probably 120, then 220 this time. You’re trying to end up with a very smooth, uniform dull layer with minimal, or no “shiny spots”
4. You may find a few areas, or the whole boat, might benefit with yet another repeat of Steps 2&3
5. You should shoot for your final epoxy sanding to be at least 220 grit before any varnish application.  A light, final 320 pass will help eliminate sanding marks.
6. Use water and paper towels to remove any sanding residue. Follow with a denatured alcohol wipe

Varnish Prep

1. Add about 3% of 333 Brushing Thinner to your Schooner Varnish, ideally directly into your new “Stop Loss” bags.  Exclude any air and cap the bag. Squeeze to mix well
2. Wipe down the boat with a tack rag
3. Add a small qty of the varnish to your paint tray, filtering as you add. You can always add more if you need to
4. Use a foam brush to very lightly varnish the hatch areas, working to their chine-like edges
5. Wet out your new West Epoxy roller, but then use the “bumpy” area of the tray to even out and remove excess varnish from the roller
6. Begin rolling on you very thin varnish layer, trying to squelch your overwhelming excitement to finally be doing this!  Work sections about 2’ in length, but across the full hull or deck width.  Try to work to a chine. Be prepared to “tip” with a dry, or fairly dry foam brush. Work quickly, but thoroughly, and with VERY light pressure. Keep moving Consider using the work lights to keep the areas lit with reflected light
7. Repeat steps 11 & 12 down the length of the boat, starting 10-12 inches from the previous wet edge, and then working toward it. Try to finish with longer, light rolling strokes to even things out. Use very light, long “tipping” strokes as well
8. Expect your first varnish layer (or two) to dry a bit rough...they are just building a base. You will be very impressed with subsequent layers.

Varnish Sanding

1. Wet sand, 400 grit - use vibratory palm sander if you can source one, or use a mini cell type foam block to hand sand....works fine, just a lot more effort. If you feel it dragging, apply more water
2. Wipe the residue with wet paper towels, then just a damp towel, until clean. Allow it to dry and Inspect for sanding uniformity (“shiny spots”). Repeat wet sanding as needed
3. Consider using the “gray, synthetic steel wool” pads to go over the hull with the RO sander, or by hand on the chines...particularly toward your later layers
4. Re-clean, including a final wipe down with denatured alcohol
5. Repeat Steps 8 - 13...try to curb your enthusiasm!

At some point, after about 4 - 6 plus layers you will step back, very pleased, and say “enough Is enough, I’m going paddling”. At that point, tell yourself “Congratulations”

Mike

Sorry, in the above note all the steps should be numbered consecutively 1 thru 19 not individually by section.  When I pasted the document I did not notice the numbering restarted in each section.

Mike

I'm happy to see this thread (and for Mike's detailed recommendations in particular) since I'm about to varnish my wood duckling.

I see that Mike recommends rolling + tipping.  At the risk of stating the obvious, presumably this is likely to yield better thickness uniformity than applying directly with a foam brush (at least for a novice).  I have a bunch of CLC's rollers but had planned to use a foam brush alone (as CLC/Nick Schade seem to recommend).  Can a novice get good results without a roller?  Either way, I think I'll "practice" on my hatch lid first (maybe on the bottom first even though it doesn't need varnish).

Yeah, practice on your hatch.

That's a good idea if you're approaching this step for the first time.

Roll & tip implies just that - roller first, bearing the coating medium, then a foam brush to 'tip' off & break any bubbles that may have formed after the roller's laid down its coating medium.

Tipping is NOT supposed to move any material that's been applied by the roller. Its purpose is to ensure that any bubbles that have formed don't remain in place long enough to 'skin over' (in the case of paint or varnish) or stay in place long enough (with epoxy) to form a fisheye or crater during cure.

Nick's got a LOT of practice! His confidence in suggesting a foam brush only may be premature for a novice to this technique.

Still, brushing can work (maybe not with epoxy, it's usually too stiff and isn't paint/varnish so it doesn't behave like paint/varnish) but I'd try the foam roller first.

Then 'tip' with a Very Light Touch of just the edge of a clean, new foamie brush for the bubble-popping pass.

One 'tip" I've learned that I can pass on is that if you hear "whale song" during the tipping pass, slow down! That sound comes from the brush vibrating as it passes along too quickly over the wet surface below and can lead to striations or waves being formed that you want to avoid. 

spclark,

Thanks for the details on rolling & tipping.  I knew the general idea, but it's helpful to know (1) that tipping shouldn't move any material and (2) that one should avoid making whale songs with the tipping brush (I remember hearing that while tipping epoxy).

I shouldn't have said that Nick "recommends" using only a brush - only that I saw him demonstrating varnishing with a foam brush alone in a how-to video.  I know he's a master boatbuilder and that his methods may not translate well to a beginner skillset, but I'm grateful to hear further support for rolling + tipping of varnish being relatively hackproof.

Rolling + tipping it is!  I'm just glad I ordered a ton of rollers from CLC a few weeks ago so I don't have to take my chances with local options.

AndrewLB, apologies if I've derailed your thread.  I'll stop here!

   @HerbieRidesAgain, et al.,   

No derailing worries - it's all been helpful.

For the record, I learned to relax and wipe up thouroughly with a couple of clean damp cloths after wet sanding, and then a tack cloth.  Original thread subject!

And based on the suggestion from @mchesser, above, when I moved on to finishing the deck, I used a roller to lay down mavarnish before tipping and found it much easier and quicker. Quicker matters on a warmish day.

Foam brushes just don't seem up to the task, the ones I've found anyhow.  Working with them on the hull I found myself holding the sponge itself (nitrile gloves on...) to accomplish anything as the brush(es) came apart by the end of a coat.   

In any event, it looks great!  We'll be on the water soon.

   @HerbieRidesAgain, et al.,   

No derailing worries - it's all been helpful.

For the record, I learned to relax and wipe up thouroughly with a couple of clean damp cloths after wet sanding, and then a tack cloth.  Original thread subject!

And based on the suggestion from @mchesser, above, when I moved on to finishing the deck, I used a roller to lay down mavarnish before tipping and found it much easier and quicker. Quicker matters on a warmish day.

Foam brushes just don't seem up to the task, the ones I've found anyhow.  Working with them on the hull I found myself holding the sponge itself (nitrile gloves on...) to accomplish anything as the brush(es) came apart by the end of a coat.   

In any event, it looks great!  We'll be on the water soon.

   Wow, such a great post it appeared twice!

   What is the purpose of the stop loss bag, over just leaving it in the original container?

Solvent-based finishes cure by evaporation of their solvents into the air as well as oxidation of some of their component chemicals when exposed to air.

That's why solvent-based finishes tend to 'skin over' after a portion of the original product has been used leaving behind greater air space. You can try to displace the air with an inert gas - typically Argon - but it's hard to achieve 100% displacement so any remaining oxygen in there will affect the leftover product.

Stop-loss storage keeps both effects to a minimum by excluding air from the container and hence from the effect of air on the contents we plan on saving for future use. No air in the container means nothing for solvents to evaporate into as well as no oxygen to combine with the reactive components in the finish product.

Rather than trying to eliminate the inevitable chemical reaction, stop-loss bags simply size the container to the volume of the remaining product so there's minimal air inside.

   nice