Epoxy coating problem

[davidpm]

What am I doing wrong. I'm trying to coat some plywood with west 105 and 205. I use a plastic scraper to spread it then tip it off with a section of west roller just like it says in the video. After the first coat dries it has tiny little sharp nubs all over.

They sand out and the second coat is better but still some nubs.

I think these pictures are after some scuff sanding so the spots show better.

[Peter HK]

The first coat of epoxy always lifts up some wood fibres from the veneer- think of painting one side of a sheet of ply; it will result in a warped piece. The same applies to the small fibres in the surface veneer- affected by surface tension effects/shrinking of epoxy on the face/ etc they tend to lift at the ends and cause little spikes.

Opinions about what to do about it vary- some say keep coating and it buries in the epoxy, others sand the first coat until smooth and then coat with little problem.

I'm not using west system so I'm not sure if there is any problem related to its usage.

The epoxy system I use has a viscosity lowering agent to add to the first coat to increase penetration- it really lifts the surface fibres but after sanding this layer it's perfectly fine.

The plywood quality has something to do with it.

Peter HK

[Tom Lathrop]

First off, it's not the epoxy, it's the wood.  Some woods are worse at this than others and individual samples are different within each species.  Here is what I do to minimize this problem and extra effort of sanding, not to mention waste of epoxy that winds up as dust.

First, sand the surface with 220 grit and clean with vacuum.  Put on the thinnest coat of epoxy possible.  Do this with a squeegee and spread with pressure to make it thin.  this will seal the fibers and won't give them enough epoxy to soak up and stand up.  After epoxy sets up hard, sand the surface with 220 grit again and recoat as necessary.  Some pieces of plywood are harder to work with than others but this method makes for less work and epoxy waste.

If there are still some fibers standing up, I usually take them off with a wood scraper.

[davidpm]

Do you tip off of just squeegee?

First off, it's not the epoxy, it's the wood.  Some woods are worse at this than others and individual samples are different within each species.  Here is what I do to minimize this problem and extra effort of sanding, not to mention waste of epoxy that winds up as dust.

First, sand the surface with 220 grit and clean with vacuum.  Put on the thinnest coat of epoxy possible.  Do this with a squeegee and spread with pressure to make it thin.  this will seal the fibers and won't give them enough epoxy to soak up and stand up.  After epoxy sets up hard, sand the surface with 220 grit again and recoat as necessary.  Some pieces of plywood are harder to work with than others but this method makes for less work and epoxy waste.

If there are still some fibers standing up, I usually take them off with a wood scraper.

[davidpm]

What system do you use and what do you thin with?

The first coat of epoxy always lifts up some wood fibres from the veneer- think of painting one side of a sheet of ply; it will result in a warped piece. The same applies to the small fibres in the surface veneer- affected by surface tension effects/shrinking of epoxy on the face/ etc they tend to lift at the ends and cause little spikes.

Opinions about what to do about it vary- some say keep coating and it buries in the epoxy, others sand the first coat until smooth and then coat with little problem.

I'm not using west system so I'm not sure if there is any problem related to its usage.

The epoxy system I use has a viscosity lowering agent to add to the first coat to increase penetration- it really lifts the surface fibres but after sanding this layer it's perfectly fine.

The plywood quality has something to do with it.

Peter HK

[Charlie Jones]

lol- I can answer that-

He uses the epoxy from Graham. And he doesn't thin it I imagine- he just puts on the thinnest possible coat- rolled out well in other words.

I do pretty much the same except I don't touch the wood with sandpaper till way later. I always use scrapers, then put on the next coat. I find it faster to use scrapers than sanding.

Both ways work- obviously ;D

But that first coat is GOING to raise nibs and bumps- little bits of wood fiber standing up- no matter what wood it is- Fir, Meeranti, Okume, whatever. Even solid Mahogany or other hard woods will have SOME of that.

edited to say-

OOPS- Just realized the question was meant for Peter, NOt Tom L. So maybe he DOESN"T use epoxy from Graham : Rest can stand as is.

[Tom Lathrop]

I have used epoxy from just abut all the well known sources and some not so well known.  Lately I use Graham's epoxy because it is so easy to get and well priced. 

Actually, the brand of epoxy doesn't matter in this case.  And no, I don't tip it out because that would not be possible.  I squeegee it on so thin that tipping would have no effect.  There will be far, far less nibs sticking up to be sanded off.

The first cost has to be very thin or this won't do what I say it will.  Squeegee, not brush, not roller and no tipping pleeze, gratuities are in included:D

Give this a try on a small piece and see if it doesn't work.  Remember, sand with 220 first, vacuum and squeegee thin---that's thin.  No! thinner than that.

A secret to using a squeegee is to have a good one.  I use a rubber squeegee from Thalco Co. 

http://surferswarehouse.web.aplus.net/Merchant2/merchant.mvc?Screen=PROD&Product_Code=rubber&Category_Code=building

OK, $24 for a 12" piece of squeegee sounds like a lot.  It will make three good sized squeegees and I have had mine for 20 years and they will go to someone else eventually.  If you forget to clean it, just sand a new tip on it.

[Guest fritzdfk]

When coating wood with epoxy you should always try to work at a constant temperature or a falling temperature. If the room temperature is rising after you coat the wood the wood will offgas and create tiny bubbles on the surface making a bumpy surface. Ideally you should heat the room/surface to get it warm, coat the surface then reduce the heat so the temperature falls as the epoxy cures. The falling temperature pulls the epoxy into the wood so no bubbles and a better coating.

[Peter HK]

David said

What system do you use and what do you thin with?

I use the epoxy from http://www.boatcraft.com.au/ as they are just down the road here in Brisbane.

Don't know what is in the viscosity lowering agent, but it's not like epoxy thinners-certainly doesn't smell like it.

Charlie said

OOPS- Just realized the question was meant for Peter, NOt Tom L. So maybe he DOESN"T use epoxy from Graham

I think the shipping costs might be a problem

Peter HK

[davidpm]

The first cost has to be very thin or this won't do what I say it will.  Squeegee, not brush, not roller and no tipping pleeze, gratuities are in included:D

Give this a try on a small piece and see if it doesn't work.  Remember, sand with 220 first, vacuum and squeegee thin---that's thin.  No! thinner than that.

Wow that worked great for the first coat. How do you do the second coat etc.?

[davidpm]

If you forget to clean it, just sand a new tip on it.

What do you clean it with?

[Tom Lathrop]

David,

Many use vinegar for cleanup and I do also.  It is not perfect but will work fine if you clean up immediately after use.  I am reluctant to use vinegar on my hands since it opens up the pores and might cause allergy problems.  Acetone is in the same category although far stronger.  Once tried to drop my Thalco squeegee in the jar of acetone with some other tools and found that it worked but soaked up so much acetone that it swelled up and became useless.  Time in the air brought it back to normal size and usefulness.

My personal cleaner of choice is waterless hand cleaner.  Favorite kind is Fast Orange.  Much better than vinegar but wont work on brushes since it is not a liquid.  All I can find these days is the hand cleaner with pumice.  Works but is abrasive on the hands.  If you forget and let the epoxy cure on the Thalco squeegee, sand it off on a belt sander or a piece of coarse sandpaper laid flat on the workbench.

After you sand the first thin coat and this should not take much effort or time, proceed with additional coats of epoxy as usual. 

[davidpm]

After you sand the first thin coat and this should not take much effort or time, proceed with additional coats of epoxy as usual. 

Does as usual mean brush, roller, squeegee, tipping, no tipping, 2,3,4 coats etc?

What about the final coat after fairing etc. Donn't have to worry about grain lifting but still wondering about your technique.

Thanks again for a great first coat technique.

[davidpm]

A secret to using a squeegee is to have a good one.  I use a rubber squeegee from Thalco Co. 

http://surferswarehouse.web.aplus.net/Merchant2/merchant.mvc?Screen=PROD&Product_Code=rubber&Category_Code=building

Is this the same thing? http://www.bodico.com/detail.aspx?ID=755

If it is it's enough squeegee to last a lifetime.

[Tom Lathrop]

It certainly appears to be and is listed as Thalco and a much better price.  They also have a 6" length for $3.95.  I'd suggest two of those 6 inchers.

ADDED:  Additional coats vary depending on the situation.  I roll and tip most of the time but will not waste a roller on a very small job where a brush is used.  The reason for rolling is to get a fair and even thickness coating of epoxy and tipping is to eliminate bubbles left by the roller. 

[davidpm]

I just got my 36" piece today. Figured I might as well as I have a son in the business and he borrows things!!

I'm used to the yellow hard plastic squeegies they have at West Marine. This is rather soft.

Are their times that the hard plastic ones should be used or are the Thaco soft ones always better?

[Tom Lathrop]

Here a couple of photos of a surface, first squeegee(ed) with a very thin coat of epoxy and then after scraping or sanding lightly.

Very little effort and the next coat of epoxy goes on smooth with no fibers sticking up.

I only use the Thalco rubber squeegees for coating and fairing jobs.  For clean-ups and such, I use the cheap plastic ones.  Plastic looses its sharp edge quickly.  I use a block plane to make a new edge.  Sanding plastic doesn't work well.  A 36" piece of Thalco squeegee should last through several generations of boatbuilders.

[davidpm]

Thanks Tom nice pictures