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Hi All,

I'm refinishing all the woodwork on the outside of the boat. Standard practices, sand down (removed all old finish), clean and wipe down with spirits, let dry, ready to apply finish.

I have a new can of Sikens Cetol Marine, applying it per instructins on the can. With a brush, I'm getting tiny bubbles. I can "brush" most of them out, but after 24 hours, the ones that remained are little "bumps" in the finish. So I lightly sand between coats, knock off the bumps, re-apply... same thing.

I'm using disposable brushes, should I be using a "good" brush? Should I apply the finish thicker? I know this is not a fine woodworking project, but since I am a woodworker (guitar builder), this is driving me nuts.

Dave
 

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Im a fan of a very very good brush and use appropriately or disposable foam brushes

bubbles can be from unsettled varnish in the can...let it sit for a while or try softer brush strokes

if its too thick from the cold it can be this too and you have to spread it more
 

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We've been using Cetol for many years and we have lots and lots of teak. We mostly use foam brushes but also use the disposable type. The problem with the disposable type is the bristles falling out. Never had bubbles. Says your in Washington State. Don't try to apply Cetol if the wood is damp or wet and you need to follow the directions for minimum temperatures for application. Chuck
 

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Discussion Starter · #7 ·
We've been using Cetol for many years and we have lots and lots of teak. We mostly use foam brushes but also use the disposable type. The problem with the disposable type is the bristles falling out. Never had bubbles. Says your in Washington State. Don't try to apply Cetol if the wood is damp or wet and you need to follow the directions for minimum temperatures for application. Chuck
Hey Chuck,

The wood is all in the garage, heated to 60-65 deg F. I hope it's the cheap brushes! And the hair falling out thing... :eek:

Dave
 

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When you say you removed the old finish, was that fully down to the grain? Zero remaining impregnation? That's a ton of work and does need to be wiped with solvent anyway. I ask because many products are just not compatible with each other.

Some less nefarious possibilities are letting the product stand for 10 or 15 mins before applying. Warm up the room to at least 70 degs, which will improve flow. Use something other than Cetol (I'm just not a fan of the product).
 

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I've never had problems with the cetol and I'm using foam brushes and second the comment about the gloss giving a more durable finish than just the natural alone. I thought it would be the other way around. The other thing that I do is to use a damp rag to wipe down after roughing up the surface instead of using a solvent. In either case make sure the surface has enough time to completely dry.
 

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Interesting problem.

I've been shaking my Cetol can to mix it, and using cheap, disposable, bristle brushes. There are bubbles in the can, but they never translated over to the wood.

Stir to mix, and use a foam brush and see what happens. I went the extra mile and used the recommended Interlux thinner, instead of just acetone or generic paint thinner. That may or may not be your problem.
 

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Bubbles can appear during the application of any coating on (POROUS) wood and whether brushed, sprayed, etc.

The usual 'cause/culprit' is SUNLIGHT and the heating of the wood surface which causes that portion of the coating that has partially penetrated to "OFF-GAS" ... and form bubbles. Once you laydown first coating which totally SEALS the natural porosity of the wood, rarely will you experience bubbles and no matter how much the sun heats the material. Its that FIRST thin coat that becomes WARMED/HOT before the coating fully sets/cures that is what causes bubbles.

The prevention: don t apply that first coat on a hot day or a day with lots of SUNLIGHT that will 'heat soak' the material under where the coating will be applied. First coats or thinned down 'spit coats' are best applied in the SHADE, and several 'spit coats' to ensure total sealing of the porosity. Once you fully SEAL the surface, then its time to lay on FULL THICK, wet coats.

Bubbles shouldnt be a problem but can cause a lot of needless extra work - resanding, filling the craters left by broken/sanded bubbles, etc. Better to put a shade over your work for the first few thinned down 'spit coats' and prevent this from happening. Even in the shade, you have to FEEL the surface temperture when applying first or spit coats .... and if that surface feel warm or HOT .... wait until a cooler time.

;-)
 

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his issue is for sure not extra heat

all temps have different applying techniques down here we thin it out more especially the first coats...if too thick basically you runover the brush strokes and get hat orange peel look from physically moving the varnish too much

use ony the thinners recomended by the manufacturer and dont abuse the percentages they say

lastly its the wood prep that counts the most
what was the last grit used to finish the wood?

I have a purdy varnish brush that is damn good and almost 20 years old...the brush is very important unless using disposable foam brushes which are great
 

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Is the solvent you cleaned the wood with compatible? Just a WAG.
this is an awesome point...I actually stopped doing the wipe with solvent or whatever to clean before the first coat...preffering actually to simply air dry and wipe with a clean new towel...

I noticed no cons to this method and never had any orange peel or incompatabilty issues from cleaning with so so solvents, acetones etc...

down here in intense tropic heat I have even washed down with water the sand finally with a very fine grit paper after sundrying

the first coat goes sun up and last before 11am or so...it will cure anddry throughout the rest of the day and then sand next morning

anywhoo
 
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I think christian.hess makes a VERY important point re: solvents and especially STRIPPERS (paint removers). If you dont remove the traces of these 'soaked-in' chemicals, either by allowing 'dry out completely' or following the recommendations for their subsequent extraction and removal, you always are at risk for - especially strippers - that are 'down deep' in the wood porosity to begin to attack your 'new' coating. When using chemical strippers, I feel, you should allow sufficient time (sometimes weeks if necessary) for these to completely remove themselves (effervescence, etc.) into the atmosphere and before apply 'new' coatings.

I have the tee shirt and sore hands/finger from applying 'new' over bare wood that I chemically 'stripped' when I 'rushed' ... and more than just a few times.

;-)
 

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Yup, could be dust too. When I did varnish work at home, I emptied every single thing out of the room and damp ragged every surface. All walls, ceiling, everything. If you have forced air heating, you're screwed! Block it off. Even convection through a window will stirs the air in the room and spread dust. It's a brutal game!
 

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I have used xylene as the preparation wash with great success, flashes off quickly and leaves no residue. I would recommend an activated charcoal respirator though as the fumes can be rather potent.
 
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