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Author Topic:   wood sealer for mahogany
PDA posted 08-10-2005 10:34 AM ET (US)   Profile for PDA   Send Email to PDA  
I am refinishing the mahogany on my 1972 Nauset. Both Z-Spar and Interlux recommend using a clear wood sealer before applying varnish at full strength. Having read the article by Brian Blazer (aka OutrageMan) he recommends sealing the wood by mixing paint thinner or turpentine with varnish for the first few coats. He does not discuss the direct application of a clear wood sealer and then applying the varnish.

My question is whether the use of a clear wood sealer and then applying the varnish coats at full strength will give a different result than mixing varnish and paint thinner prior to applying varnish at full strength?

Is there any benefit to using both methods before applying varnish at full strength?

Any advice on these questions will be appreciated?

bsmotril posted 08-10-2005 11:07 AM ET (US)     Profile for bsmotril  Send Email to bsmotril     
You will get a better surface bond, and penetration into the wood using thinned varnish. Thus, the surface will last longer and take more abrasion before the film fails. But, an even more durable alternative is to use a clear penetrating epoxy coat first, 2 coats, followed by 4-6 coats of varnish. That is about equal to 8-12 coats of varnish in durability and longevity. West Systems makes such epoxy. Make sure to get the hardener/catalyst specific for the clear coating application. other hardeners dry yellow to amber versus clear.
BillS
Flex Tuning posted 08-10-2005 01:20 PM ET (US)     Profile for Flex Tuning  Send Email to Flex Tuning     
PDA, I used Epifanes bootlak with the the thinner. 1st caot 50/50, 2nd-75/25 and then 3 or 4 more coats full strength. It looks great! but I will warn you once you see a little decay in the finish don't put it off recoat right away. As fo rhte west epoxy stuff, I think that that is what I caoted the edges of my plywood with when I built the console. It is definitely bullet proof but looks much darker IMO.
PeteB88 posted 08-11-2005 12:53 AM ET (US)     Profile for PeteB88  Send Email to PeteB88     
I've done all this stuff many times. Sanding sealer, sealer etc is most likely thinned varnish - as indicated. Don't drive yourself nuts doing this. Certainly the epoxy base coats are a great idea if you feel like doing it. However, the wood must be totally clean and free of any solvents or oils.

The rule of thumb is to recoat with the object loses 50% of its gloss. All you have to do is simple scuff sanding, remove the dust w/ vacuum and clean rags and apply the finish.

The big deal is proper prep, tools/supplies and allowing for curing time. I let each coat fully cure - that is determined best by using a piece of sandpaper to test if ready. If you scuff the object it is ready to scuff sand if the varnish "powders" as opposed to a resiny build-up on the paper (gummy) also referred to as "loading up the paper" This is important.

good luck -- ask questions.

RocketMan posted 08-11-2005 10:17 AM ET (US)     Profile for RocketMan  Send Email to RocketMan     
What about the application of 'grain filler' ?
OutrageMan posted 08-11-2005 01:09 PM ET (US)     Profile for OutrageMan  Send Email to OutrageMan     
As the saying goes, "I don't paint with glue and I don't glue with paint."

Epoxy has no UV protection in it. As you build your coats with spar varnish, you are building UV protection. If you use epoxy first, it is my opinion that not only do you need to protect the wood from UV, but the epoxy as well. And if the epoxy goes, there goes the whole show.

I have used grain fillers on furniture that I have made and it works well. I do think that it is possible to get away with not using it on marine brightwork due to the number of coats of varnish that are usually applied. As you lay down coats in the beginning you are filling voids and then sanding to level the surface. After 4-6 coats you should have a very level and well built up surface ready for the "candy coats."

Brian

PDA posted 08-11-2005 03:03 PM ET (US)     Profile for PDA  Send Email to PDA     
To all who responded to my inquiry about sealing mahogany, thanks for your advice. I spoke with the technical staff at West Systems regarding the use of Varnish over Epoxy and inaddition to their explanation of the benefits of using Epoxy under varnish, they referred me to an article written by one of their staff, Tom Pawlak. You can find it at www.epoxyworks.com then click on articles by subject; then click on epoxy techniques & materials; then click on varnish over epoxy (#18). The article makes a good case as to why epoxy and varnish work well together in terms of protecting against stretch/shrink cycles and oxidation from exposure to the sun's UV light. In this approach epoxy protects against the stretch/shrink cycle and varnish protects the expoxy from the harmful effects of UV radiation. As the article outlines the two in combination are betterthan each coating by itself.

The approach of varnish over epoxy is also less work because fewer coats of varnish have to be applied.

If anyone decides to use this approach other pointers that were made to me in the discussion were as follows:

1. use a stiff brush to apply exoxy and it helps to cut off some of the paint brush bristles to make it stiffer.

2. Make small batches of epoxy because after 15 to 30 minutes the epoxy becomes more difficult to work with.

3. Use a metering pump to mix hardner and resin at a 3 to 1 ratio. This a more precise way to measure.

4. Use latex gloves when working with epoxy.

5. For further info on applying epoxy read "wet sanding epoxy" # 17 & Avoiding surface contamination #20.

I appreciate all the advice on the best methods for applying varnish. This is the first time I have undertaken this type of refinishing effort and I am giving very consideration to using the approach of varnish over epoxy because of how they complement each other.

Robob2003 posted 08-11-2005 03:04 PM ET (US)     Profile for Robob2003  Send Email to Robob2003     
I agree with OutrageMan.

I did 12 coats of Flagship spar varnish, the first 4 coats thinned 50%, the next 4 20% and the final 4 full strength sanding lightly after all but the last coat and I am pleased with the results.

Make sure it's strained each time you apply a coat.

I have a before and after pics on my homepage

Bob on Tampa Bay

Chesapeake posted 08-12-2005 01:40 PM ET (US)     Profile for Chesapeake  Send Email to Chesapeake     
Don't know if anyone on this site has ever tried this... but it is "the answer."

Use first two coats - Awl-spar. This gives the nice amber glow. Subsequent coats with Awl-bright - a two part, clear polyurethane finish from US Paint (makers of Awl-grip). Bulletproof finish with the look of classic spar.

It ain't cheap and it ain't easy. But neither is redoing your brightwork. It looks fantastic.

OutrageMan posted 08-12-2005 01:50 PM ET (US)     Profile for OutrageMan  Send Email to OutrageMan     
I am a big fan of the 2 part coatings. Mostly because several coats can be applied while previous coats are still green, and they do offer substantial durability increases over traditional spar varnishes. All this comes at a cost, however. If you do not keep up with regular maintenance, and cracks or chips appear, you can not re-coat these areas. Additionally, should the product need to be removed, it must be done so with mechanical means only because there is no stripping product that will touch them. When you have to go after it with sandpaper, you will then see just how tough this stuff really is.

Brian

PeteB88 posted 08-15-2005 10:48 PM ET (US)     Profile for PeteB88  Send Email to PeteB88     
For what it's worth -- Could be a song title!

WEST procedures are accurate and most significant for soft wood like D. FIR marine plywood - - using West and light fiberglass cloth eliminates checking on marine ply.

Hardwood, like the outstanding materials sourced for Boston Whalers, is much more stable and resistant to checking - but it will crack and check esp at end grain if not protected.

As regards grain fillers: I assure you that unless you are talking about severe checking or cracks multiple coats of marine spar varnish will fill the grain of mahogany. Moreover, application of marine spar varnish will indeed raise the grain which is smoothed by scuff sanding between coats. Varnish is very cool.

bullwinkle posted 08-16-2005 11:44 AM ET (US)     Profile for bullwinkle    
This is all very interesting and informative. There is no mention of spar urethane for this purpose. I just finished a large room at home with it and intend to use the leftover for the 13 woodwork. Is that a mistake?
Mike
OutrageMan posted 08-16-2005 11:57 AM ET (US)     Profile for OutrageMan  Send Email to OutrageMan     
I am not sure about 'spar' urethane, but typical urethane is a bit too stiff and cracks more easily under the pressures of hydraulic cycling than does a true spar varnish.

Brian

Binkie posted 08-16-2005 12:44 PM ET (US)     Profile for Binkie  Send Email to Binkie     
Chesapeake' your method really is "the answer", for durability and looks, and is the product and method used on most high dollar wooden sport fishing boats. where money is no object.
Just like most everything, if you demand the best, its going to cost you more, but the results may be worth it. There may be many alternatives and "tricks", around but in my mind they all come up short when compared to any Awlgrip product.
PeteB88 posted 08-20-2005 12:03 AM ET (US)     Profile for PeteB88  Send Email to PeteB88     
Spar varnish- boat goes faster and you catch more fish if you use it. The stuff works esp on marine mahogany. IT is EXTREMELY easy to fix if it gets scratched or gouged. If you have to you simply scuff the area with sand paper and put some on. I used to use marine oils - teak, linseed mix homemade etc and just wiped over the scratches ala Homer Formbee but better stuff for marine. If you wipe some oil over a scratch it disapears - - almost totally. It protects any expose wood if deep and you can go as nuts as you want to repairing.
it is much more difficult to do that w/ 2 part paints and clear finish but they are supposed to be harder.

Varnish. It is nice.

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