# Exterior primer for genuine mahogany



## Redux (Oct 27, 2018)

Wondering what would be your choice of exterior primer for genuine mahogany tongue and groove vertical siding. I’m not too up-to-date on exterior products/finishes. The finish spec calls for Aura Exterior Low Luster Kendall Charcoal. 

I originally joined this site having an issue with cedar siding which is now being changed out for genuine mahogany. Everything will be shop primed for a winter installation, not being able to be finish coated until mid-March. 

Just wondering what you would use...2 coats primer? 1st of 2 finish before installation? No finish before installation? Brand/type? 

I’m all ears on any suggestions.


----------



## Woodco (Nov 19, 2016)

Painting exterior mahogany, huh? Weird. I would spray and backbrush one coat of exterior oil, and one coat of finish, since it will sit until march. Then do one more when its up, and you can. I wouldnt think more than one coat of primer is necessary, unless you see a bunch of tannin bleedthrough after the first one. No idea how mahogany does painted, myself.


----------



## cocomonkeynuts (Apr 14, 2017)

Not sure what mahogany species you have, if its particularly oily or not but acetone wipe, prime with BM100.


----------



## Redux (Oct 27, 2018)

Swietenia macrophylla, the real deal. Plantation grown in Fiji after WWII so it’s not fully developed and not too oily.

With the 100 would you recommend the stock gray or the deep base tinted? The Kendall Charcoal is very dark. I’ve received mixed review from 2 BM tech reps and retailers on the deep base, telling me that too much colorant could possibly result in prolonged drying...??

I did make up 4 samples and left them outside for a month. I used one coat of Arbor Coat 366 deep base tinted as per one of the retailers suggestions and 2 finish coats of Aura. I “did” get a considerable amount of tannin bleed on one board. I’m worried ‘cause the siding will die into white limestone pavers. Do you think that one coat of the 100 will block the tannins better than the 366? Any thoughts on 2 coats of the 100? Ridiculously long time to dry? Not that we’re allowed to thin the first coat...wink, wink..
Finish sand to what grit?

Sorry for all the questions, exteriors not being my regular gig.

Honduras Mahogany used to be cheaper than clear white pine up until 1990, and was the go-to paint grade exterior wood in my region. Now you can’t get it. Kinda sad seeing such a beautiful wood depleted for such purposes.


----------



## cocomonkeynuts (Apr 14, 2017)

Adding lots of universal colorant extends dry time of course. I would use the stock grey 100 underneath Kendall charcoal. You can also add 1-2oz colorant if you want to get closer to the final color but 2 coats of aura or mooreguard will cover that no problem. 366 primer is pretty much relabelled 094 primer. Same thing I tell most other contractors. Test for moisture content. Sand 80-100 grit then prime all sides including end grain. Holding 40+ degree and <70% humidity for atleast 24 hours. I would still do an acetone wipe to remove any residual oils near the surface that also tend to extend the dry time of oil based coatings. I would be very surprised to see any tannin bleed.


----------



## Redux (Oct 27, 2018)

Figured I’d post this for informational purposes in the event anyone here experiences a similar problem. Below are photos of the cedar scheduled for replacement due to repeated finish failure, having been stripped and refinished as many as 5 times in 4 years by three different contractors. The primary failure is due to extremely high levels of essential oils found in blonde outer butt heartwood in WRC. The secondary failure is due to a condition known as bacterial wetwood.

The first pic illustrates oil migrating through the oil primer in the form of the small white lines.

The 2nd pic illustrates the oil after it evaporates, the eruption sites and cratering in the prime coat resembling solvent pop.

The third pic illustrates wetwood exudate, the primer on the board with the arrow not drying down, re-wetting from the exudate which turned the primer gummy, leaving a sticky film on the board faces beneath the primer. The boards were all the same color after intercoat sanding, the wetwood boards becoming darker after one day.

The fourth pic illustrates wetwood exudate, checking moisture contents. Trapped moisture in wetwood occurs in pencil thin lines along the growth rings and is very difficult to detect. Unless the probe hits the lines with trapped moisture, it likely won’t register. 

The 5th pic illustrates the 3rd removal/refinish. Everything was sanded down to #120, vacuumed, double wiped with acetone, primed with BM 100, and still failed. Nothing was exposed to weather, low temps, direct sunlight, or high humidity. Everything was back/edge/butt primed, installed over cedar breather.

The 6th pic illustrates blistering as a result of the highly volatile essential oils.

The homeowner was convinced that every possible remedy other than a tear-off had been executed. 

I’ve “never” seen this happen with cedar.

Some coatings and adhesive manufacturers have been reporting failure on ~ 20% of WRC as a result of the essential oils. It seems to be a fairly new problem.


----------



## Woodco (Nov 19, 2016)

Wow. So, its basically unpaintable wood? I wonder if those paint contractors got paid or not...

Does anyone put anything in their contract about waiving responsibility for bad wood like that?

Also, did they ever try a solid color stain instead of paint?


----------



## cocomonkeynuts (Apr 14, 2017)

Woodco said:


> Wow. So, its basically unpaintable wood? I wonder if those paint contractors got paid or not...
> 
> Does anyone put anything in their contract about waiving responsibility for bad wood like that?
> 
> Also, did they ever try a solid color stain instead of paint?


I wonder how a penetrating epoxy sealer would work on that stuff too


----------



## Redux (Oct 27, 2018)

cocomonkeynuts said:


> I wonder how a penetrating epoxy sealer would work on that stuff too


Funny you should mention that...great call! 

I shot the chemist for CPES an email describing the condition a few weeks ago, and I’m going to be stripping and refinishing all the facia this spring which is experiencing the same problem. I’m going to try the CPES/Clear Penetrating Epoxy Sealer, it being used on boats for old growth Bald Cypress, WRC, and AYC for the same reasons. I had started a thread about CPES on this site for oily species such as Sinker Cypress. I didn’t get any responses 🤔

I was reading an article by Western Canada’s Forestry Products Lab on the issue as well. The article suggested air seasoning, a very specific kiln drying schedule, chemical extraction, and sealing with a thin impregnating phenolic resin varnish. The article was written prior to the introduction of CPES.
@Woodco, everyone did get paid, however, I’m not certain if the first contractor got paid for the first removal. I was the third contractor being paid to problem solve...I didn’t have the conscience to submit an invoice for the work. The customers being two of the finest people I’ve ever met did send me a nice check though.. I never had an exclusion clause for finish failure due to wood issues except for veneer and shake. I would definitely consider specific wording in future contracts indemnifying me. 

Stain was discussed yet wouldn’t work with the design. I also opted not to bother trying the CPES on the siding because the nickel gap was getting clogged up with paint. All were on the same page with changing it out, milling the tongues wider than the grooves, to maintain a nice clean serviceable reveal.


----------



## Tprice2193 (Oct 3, 2017)

@Alchemy Redux "thin phenolic resin varnish" Waterlox Original sealer?


----------



## cocomonkeynuts (Apr 14, 2017)

Alchemy Redux said:


> cocomonkeynuts said:
> 
> 
> > I wonder how a penetrating epoxy sealer would work on that stuff too
> ...


BM has a similar product V155. Check your PM I'll send you some contact info...

Maybe even a poduct like Daly's shipnshore would be enough to seal it. It is a penetrating urethane resin instead of epoxy.


----------



## Redux (Oct 27, 2018)

Tprice2193 said:


> @Alchemy Redux "thin phenolic resin varnish" Waterlox Original sealer?


Yes, most of the Waterlox products are tung oil formulated/phenolic resin varnishes with ester gum. I’ve used Waterlox a lot when finishing reclaimed Carlisle Wide Plank Flooring. I “believe” the Carlisle Tung Oil was just Waterlox rebranded, although I probably wasn’t supposed to tell anybody that...


----------



## Redux (Oct 27, 2018)

cocomonkeynuts said:


> BM has a similar product V155. Check your PM I'll send you some contact info...
> 
> Maybe even a poduct like Daly's shipnshore would be enough to seal it. It is a penetrating urethane resin instead of epoxy.


Ha! I like your thinking...I brought the V155 up in conversation 3 weeks ago with a BM retail manager with the suggestion of rebranding it to provide a competitive solution to other brands such as CPES. It serves as an anchor coat for concrete, so why not wood? .... same chemistry as CPES, no?...It should volatilize moisture, sap, oils, and the drying/curing shouldn’t be affected by any residual oils in wood. 
Again, another great call by you!


----------



## cocomonkeynuts (Apr 14, 2017)

Alchemy Redux said:


> cocomonkeynuts said:
> 
> 
> > BM has a similar product V155. Check your PM I'll send you some contact info...
> ...


I like that stuff because it really penetrates and drives out latent moisture in the substrate. Also because of its low viscosity it is able to penetrate and encapsulate rust when it's not economiclly feasible to remove all before coating. Also serves as a tie coat between previous finishes and can be topcoated with pretty much anything.

I sell tons of that product not much for wood though, hard sell when the TDS doesn't mention wood substrate anymore. I agree with rebranding it... The old TDS used to have a section for wood and it still mentions it on the can but removed from the current TDS.


----------



## PNW Painter (Sep 5, 2013)

I’ve never used the V155, but I have used CEPS on a couple of Fir doors and for priming some wood windows.

The consistency of CEPS is similar to water. It penetrates into the wood very well and I’m guessing that it would work well with mahogany. If you search around some boating forums you could probably find some specific info in terms of compatibility with mahogany.

Here’s a little CEPS mini review.
- Easy to apply. I found that foam brushes work well. In case it matters I don’t think it can be sprayed.
- Once cured the surface becomes extremely hard. This could be beneficial for softer woods, such as Fir.
- CEPS seals surfaces so well that paints or spar varnishes will take longer than normal to dry.
- The smell is really strong. I’d recommend wearing a respirator with the appropriate cartridges.
- CEPS is expensive, but a small amount covers more surface area than you’d expect.
- There is a summer and winter formula. 
- Can be used as a primer for clear finishes. 

CEPS is well know in the marine industry and is typically applied prior to applying spar varnishes.

Also, I first learned about CPES from a GC who hired a company to build a huge custom bay window on-site. He said they prime all the raw wood on every window with CPES. 

Hope this helps.




Sent from my iPhone using Tapatalk


----------



## Redux (Oct 27, 2018)

@ PNW Painter

Thanks for the useful tips. I think we’re both referring to CPES by Smith’s, and yes, a boat builder suggested it and the boat forums were very helpful. 

The guys at the paint store and myself were looking through the tech info on the V155 a few weeks ago and it made no mention for wood substrates as mentioned by Cocomonkeynuts, although it is wood compatible. 

I’m going to try sampling both the Smith’s and the V155 and see how they work.


----------



## cocomonkeynuts (Apr 14, 2017)

Alchemy Redux said:


> @ PNW Painter
> 
> Thanks for the useful tips. I think we’re both referring to CPES by Smith’s, and yes, a boat builder suggested it and the boat forums were very helpful.
> 
> ...



The old TDS and the actual cans mention wood substrate. They removed it in the new TDS for marketing reasons. More industrial uses for steel/masonry.


http://htdpaducah.com/Corotech%20Concrete_files/20140923_Corotech_V155_TDS_EN_OKF.pdf


"Wood: Apply 1 - 2 coats of V155, brushing out any puddles left after 30 minutes.


----------



## Redux (Oct 27, 2018)

@ Cocomonkeynuts

Thanks! I’m becoming visually impaired with old age, reading glasses no longer cutting it. I often struggle reading the labeling on cans...most likely going to use the V155 as per your suggestion. I’d just like to test the two for viscosity.


----------

