Thinning Epoxy to Penetrate Wood.

[sobraon]

Mark,
I posted the previous post and then saw you had too.

Just as another issue.

When I did the saloon table I used 2pac poly for added strength.

I am not sure that this is still necessary. On the sole in the aft cabin we have applied a single pack poly and it is standing up well to wear and tear.

It is certainly a lot easier to apply.

Unless you intend to have a lot of dancing on the table the single pack should be fine.

Garry
Spirit of Sobraon
Home Page | Spirit of Sobraon's Travel Log

[thinwater]

Originally Posted by sailing_jack

Wet on wet refers to ensuring a chemical bond as opposed to a physical bond.

After the coat has 'kicked' ie it is no longer liquid, but still wet, then add another coat. Since the first coat has not fully cured, the layers bond chemically.

If the coat is fully cured, then you have to sand to give the next layer some 'tooth' to physically bond to.

The chemical bond is stronger.

Don't try to add more while still liquid (before it kicks) you will make a mess.

This does not apply to penetrating epoxies. Yes, I have spoken with several makers. The chemistry is too different. You have to wait for a full cure (about 2-4 days depending on temperature, scrub off the blush, and then sand.


I am also gluing some test blocks, to see how bonding compares.

[Pauls]

The addition of large amounts of solvents, ie acetone, to epoxy results in an epoxy which never hardens well and is not very effective as a sealer. Mix up a sample and see the results for yourself.

Talking with the tech guys at a major epoxy manufacturer, 10% added solvent will still result in a good cure. For sealing surfaces with epoxy I highly recommend the Low Viscosity Epoxy available from Progressive Epoxy Polymers. It is a 100% solids epoxy, ie no solvents added, and is by far the lowest viscosity epoxy I've ever seen. I add 10% solvent to this, it penetrates wood very well and fully cures to a hard condition.

[majnun]

Personally, I use CPES (Clear Penetrating Epoxy Sealer) from Smith & Co. Been their customer since 1993.

[Pauls]

Have you mixed up a sample in a cup and let it cure? If it is anything less than fully hard its sealing ability is compromised. Most of the "epoxy sealers" or "penetrating epoxies" are just plain epoxy resin with a large dose of solvent added to thin them down. Ones I've tested cure to a kind of stiff jello consistency.

[Bowdrie]

Originally Posted by majnun

Personally, I use CPES (Clear Penetrating Epoxy Sealer) from Smith & Co. Been their customer since 1993.

Originally Posted by Pauls

Have you mixed up a sample in a cup and let it cure? If it is anything less than fully hard its sealing ability is compromised. Most of the "epoxy sealers" or "penetrating epoxies" are just plain epoxy resin with a large dose of solvent added to thin them down. Ones I've tested cure to a kind of stiff jello consistency.

Sorry, the "just plain epoxy" is totally wrong, so is the part about the "jello".
The CPES when used as designed gets quite hard.
It's NOT formulated to just pour into a void. it IS formulated to soak into wood where it DOES harden.
Have used uncountable gallons of "Smiths" since the '80s, it has always done what it was formulated to do.

[majnun]

I use CPES primarily as a sealer for furniture making. When I am ready to apply a finish, I apply CPES liberally then I wipe it down with a rag wet with alcohol. This removes the epoxy from the surface leaves the top pores of the word open for oil, polyurethane or paint. It prevents stain becoming blotchy. I've also used it to combat dry rot on wooden boats of mine. It hasn't let me down in all these years. I also like the owner and genius behind the product, Steve Smith. His laminating epoxy resin and glues work well. They've always kicked off and held. Can't say that about other brands.

[Terra Nova]

Originally Posted by Pauls

...Most of the..."penetrating epoxies" are just plain epoxy resin with a large dose of solvent added to thin them down...

A shame for this type of misinformation to be spread.

[s/v Jedi]

I only used the TotalBoat penetrating epoxy and have further thinned it as much as 40% with alcohol conform instructions.

Regardless of amount of alcohol thinning used (or none at all), cured result is the same: a fully cured flexible type of epoxy in the tub and a rock hard surface where it penetrated plywood. After sanding away any excess/pooling epoxy on treated plywood, it looks like wood but feels like a hard, smooth fiberglass surface.

I can believe that thinning regular epoxy doesn’t work.

[Pauls]

As regards several of the negative commenters above, did any of you notice that I did not name CPES? I've never used it. However, I have tested Git Rot and another brand the name of which I do not recall. Both showed the results described. The point of the post is to test the hardening ability of any penetrating epoxy with which you are not familiar before using it on your boat.

[thinwater]

Originally Posted by Terra Nova

A shame for this type of misinformation to be spread.

True ... sort of.


Most (all?) penetrating epoxies contain non-reactive, non-volitile components to achieve the low viscosity. This allows them to call them 100% solids, even though as much as half is not part of the crosslinked polymer. If you look up the strength specs (unless they chose not to publish them) they are about 5 times weaker than conventional epoxies, with tensile strengths around 1000-1400 psi. That is a fact that you can Google, and if you find a stronger penetrating epoxy, please post that.


Many also fail to post viscosity. I found that particularly ironic when I googled the "low viscosity epoxy" linked above. No technical specs. If a manufacturer can't be bothered or is for some reason afraid to post basic technical specs, I don't know what I'm buying and will go elsewhere.

[Bowdrie]

Originally Posted by thinwater

If you look up the strength specs (unless they chose not to publish them) they are about 5 times weaker than conventional epoxies, with tensile strengths around 1000-1400 psi. That is a fact that you can Google, and if you find a stronger penetrating epoxy, please post that.

I can only speak to the CPES made by Smiths.
And they are quite up-front in the literature that the product is not a "glue".
If it's not a glue how strong does it need to be?
I've found that one of its best uses is as a sealing primer on wood that is to be varnished or primed/painted, or as a sealer on wood that will have some kind of "stuff-in-a-tube" applied.
The old regimens of thinning varnish with ever decreasing amounts of thinner over a million coats to seal the wood is mostly an exercise in futility, (But it sure helps the varnish people present big bills to the client).
No varnish or paint, no matter how much thinner you put in it will penetrate much beyond the first layer or two of un-broken cell structures, and neither will any epoxy glue.
The CPES will penetrate further and leave a surface that requires minimal work before you can start laying-on real coats of product.
The caveat? you have to keep putting it on until the wood will not absorb any more, and not allow it to dry between applications.
As always, the manufacturer's instructions generally take priority over the "enlightened ideas?" of the end user.

[thinwater]

Most manufactures post technical specs. I've used CPES. No magic, IMHO, just mystery.



I prefer to buy products with technical specifications. Even varnish has standard specifications for viscosity and tensile strength.