Soft wood epoxy soak

[nedgrater]

This is a bit of a random one, but I want to reinforce soft wood with epoxy to make it harder, the wood I am using is poplar and is 1.5mm thick.
The problem I have is that the epoxy just sits on the surface of the wood and doesn't penetate and give the wood any aditional structure.
What i want the epoxy to do is to soak in and really make the wood hard, how can I do this?
I have tried thinning the epoxy with denatured alcohol but this still isn't very effective. I wonder if heating the epoxy or wood would help create better penertration.
Can anyone offer any advice on my sticky situation!:)

[marshmat]

Nedgrater,

Are you trying to give the wood a harder surface for dent resistance (ie, a table top) or are you trying to make it stronger?

A hard surface might be achieved with some thin (say 4 oz) fibreglass cloth set in epoxy; this is light enough that it should still look like wood. Straight epoxy should soak into the wood enough to seal it and keep it from getting wet, but won't add much if any structural value.

Cutting your epoxy with solvents is unlikely to work too well; it may thin the resin, but it'll also weaken it, defeating the purpose. Heat can sometimes lower the viscosity of freshly mixed epoxy, but also greatly accelerates the curing process.

[peterAustralia]

what about CPES

clear penetrating epoxy sealant

[Squidly-Diddly]

epoxy into it. Vacuum to force liquid into porus wood sounds a little counter-intuitive, but that is how they tread wood of knife or gun handles.

Not sure of the exact process or if they are using 'normal' epoxy, or if this method works for boat sized lumber.

I bought a thin(like water almost) clear epoxy in a 8 oz bottle that is supposed to be for making dry-rotted would all epoxied and sound. I never tried it on anything.

I have a hard time imagining regular epoxy getting more than 1/8" in most wood before hardening.

[catsketcher]

The idea of getting epoxy to suck itself into the edge of grain is not something I have ever seen. Epoxy when warm can certainly get thin and then suck up end grain. This is certainly an effect you need to consider when gluing scarf joints that show exposed end grain. Think of wood as a collection of straws. You can easily get epoxy up the ends but getting it in between the straws is basically impossible to any depth.

As for vacuum bagging, I don't wish to seem rude, but I can't see how this could help. Bagging is usually used to remove epoxy from a laminate. I have never heard of it being used to push epoxy into wood. I do a fair bit of bagging (just did one yesterday) and it makes great laminates.

If the idea is to harden the timber use a very light layer of fine cloth. Adding epoxy on its own will do very little to increase the mechanical properties of the timber without glass.

cheers

Phil

[catsketcher]

As Mashmat rightly said don't thin epoxy. Use heat to thin it. Make small mixes and warm it up to make it runny but don't ever alter the ratios and stay away from thinners.

One reason - there are many different types of epoxy and it takes a chemist to work out what type uses what reducer
and two - the thinners like Toluene are cancer causing chemicals. Stay away from them. Throw away brushes and clothes or use white vinegar

[PAR]

As has been mentioned, heat is the best way to get better penetration, not thinning the epoxy, which just weakens it.

I suspect if you are having difficulty with penetration, there's something sealing the surface, preventing it.

It would be helpful if you offered additional information about what you're trying to do. Plus the state of the wood. We know about the rot, which we can assume is a pocket or an affected area. Is it painted, varnished, treated with wood preserver, etc. and other such bits about it's condition.

[nedgrater]

Wow thanks for all the feed back!
I am trying to gain dent resistance rather than over all strength of the wood, but am reluctant to use a cloth as I want it to look like plain wood.
It sounds like the general idea is that I should use heat rather than thinners.
I had an idea about how i maybe could do this-
Mix some epoxy at a good working temperature, then when the epoxy is on the surface of the wood, heat the wood so that the epoxy soaks in due to the lowered viscosity. While the epoxy is still uncured repeate the process so that as much epoxy is absorbed into the wood as possible.
Thats the plan anyway, I think i'm gona give it a go and see how I get on.
The wood I'm using is new wood.
I too cant see the vacuum method working, I thought the reverse may work though- a pressure chambre, but this seams like alot of effort and the results maybe negligable.
I'll do some tests today and post my results tommorow.
Thanks:)

[PAR]

Rather then making all these grandiose guesses at treating this wood with epoxy, how about absorbing a little information, before you make more mistakes.

Log onto www.westsystem.com and www.systemthree.com and have a look at their user's guides. It discusses their products, applications, techniques, etc. With this information you'll at least have a level playing field and not be wasting material and time trying different things.

I mention this because, if you heat the wood while the epoxy is on it, the wood "out gas" and you'll have bubbles all over the surface.

If you use fabric (cloth) weights 4 ounces or less, you will not see the weave once the epoxy wets out the fabric.

The vacuum methods hinted at previously, will work quite well for you application as we understand it, but does require some specialized equipment and supplies that you may not have.

How about some specifics, what species is the wood? Have you sanded it and with what grit? Is the wood treated in any way? What are the average temperatures you're working in? What brand of epoxy and the hardener type (speed)?

[AndrewK]

Epoxy will only soak approx 80 microns into side grain and only 2-3 mm into end grain in light soft wood, less in dense wood.
This is why it is possible to infuse end grain balsa at 100% vacuum without filling the core with resin.
You will get better results with low viscosity resin like infusion grade as this resin has higher concentration of reactive diluent, not solvent.
Also heat the timber prior to applying epoxy so that it draws the epoxy in as it is cooling and not the other way around as already mentioned.
I go along with the recommendations to use a light weight glass like 200gm2 plain weave, do a test piece and you will be surprised how translucent the glass is.
If you do not want to use glass then you will need to build up the neat epoxy to a reasonable thickness with a number of layers. Floor surfacing epoxy should also be best choice as it is harder than marine epoxy.

[lewisboats]

poplar...not the best of boat woods.

[Squidly-Diddly]

It wasn't how they did it commercially, just for demonstration purposes.

They had a block of wood about 6" covered with epoxy in a vacuum chamber with a window. They turned on the vacuum and at a certain point bubbles began to emerge from the wood, and at a certain point they dwindled. Not much movement from the surface of the epoxy. Apparently the air and ANY WATER was being removed and replaced with epoxy.

The water was being removed as it boiled in the low pressure. I guess epoxy doesn't boil in low pressures like water.

I'm not sure if this would work with a bag, or how it is done commercially.


Here is "resin infused wood handles" knife:

This stuff all looks laminated, though.

http://www.rutply.com/products/dymondwood-gallery.html

[nedgrater]

I did a test peice today in the way I described in my last post and am waiting for the epoxy to cure.

The vaccum is an interesting idea and now sqidly-didly explained how it may work, it now makes more sense to me, (sorry for dismissing it earlier).
As far as I can picture it if epoxy is sitting on the surface of the wood and then the vaccum removes air from the wood the epoxy should be forced into the vaccum spaces in the wood.
I have actually got vacuum equipment, so I am quite keen to give this a try, but would be grateful for any tips or tecniques before I do.
The epoxy I'm using is Resin Research epoxy.
Thanks for all your help so far guys...

[rwatson]

If a clear high gloss finish is essential, make sure you use the correct Hardener. West Systems 207 hardener is the only one they recomend for really high quality finishes. It costs more than the resin, so it better be good.

[nedgrater]

I did a test peice, by heating the wood, applying warmed epoxy and the heated it further still, I did this a second time then let it cool and cure.
When it was cured I sliced the timber in half to see how far it had penetrated, and it had gone down about 1mm.
The poplar timber I am using is only 2mm thick.
I was fairly pleased with the results, and it made the surface of the wood fairly dent resistant.
I haven't yet tryed the vaccum method, but plan too in the next few days to see if I can get a better result again.
I belive that as a few of you have described by heating the wood you are releaseing water and air from the wood, if the warmed epoxy if then applyed and the wood allowed to cool, this I imagine will have a similar effect to a vaccum as it would pull the resin into the voids created by the cooling wood.
If the results from the vaccum method are fantastic, I will use that but if the results are not very different from the heating method I just described I think I will stick to that, as its a pretty user friendly and quick process.

[PAR]

Rather then making all these grandiose guesses at treating this wood with epoxy, how about absorbing a little information, before you make more mistakes.

Log onto www.westsystem.com and www.systemthree.com and have a look at their user's guides. It discusses their products, applications, techniques, etc.

As I mentioned in a previous post. Reheating is self defeating and likely driving out resin, not letting more in. I guess it depends on how badly you'd like this to succeed.

[nedgrater]

Test results-
In short the vaccum method did the job.... brilliantly.
Thanks for the help as it really wouldn't have occured to me to use this method.
I was particually suprised because I have vaced on balsa before and don't remember the balsa skins becoming satuarated.
I did a few different tests and as most of you said penetraing epoxy does nothing for strength... True.
I think the exact method I will use when I do it for real is to heat the wood before I epoxy, to drive out any moisture, warm the epoxy so the viscosity is a little less then apply very librally to the wood, then get it in the bag asp.
The test peice was so good the 2mm poplar wood was 100% saturated and tough as old boots.
many thanks I'm a happy man!

[Squidly-Diddly]

for the same reason that using a vacuum starting at low pressure would be less effective.

Less 'air' to replace.

[nedgrater]

Hey Squidly Diddly, Wow, I think I follow what you saying.... This is crazy stuff!
So if I pressurize the wood in a chamber before painting with epoxy and putting in a vac bag the vaccum would be more effective....
This had definatly never occured to me.
Wouldn't the whole room need to be pressurised though because as soon as you take the wood out of the chamber the pressure would release back to your local atmospheric pressure and the vacumm not be any more effective, or would the wood stay pressurized some how?
This is a very interesting concept though, have I got the gist of what your saying or am I off track?

[rwatson]

I have no idea what Mr Sq was trying to say, but if you take the wood out of a Vac, it would not "stay pressurized some how"

But I think it would have removed a lot of the water already, so during the "real" pressurisation that should allow an even better penetraton I would suspect.

I am following your experimentaion with real interest. What it would mean is that a lot poorer woods can be used for boatbuilding, and considering the prices of "good" woods, that aint a bad thing

[PAR]

To dispel some disinformation and misunderstanding of what is actually happening.

In a vacuum bag you aren't placing the goo in a "suction" type of environment, you are placing it under pressure and frankly lots of it. The pressure comes from the atmosphere bearing down on the bag. Pulling 15 PSI on a pump seems like it's not much, but it's over one atmosphere and if you think about it differently, it's over a ton per sq. foot (2,160 PSI). Now that is a lot of pressure.

Heating the wood causes the wood and the things inside the wood to expand. When epoxy is applied and most importantly (as I mentioned earlier) the wood is cooling down, the now contracting wood fibers and cellular structure will draw in epoxy, if it's viscosity is low enough.

You can improve (lower) the epoxy viscosity by heating, of course at the risk of kicking it off much faster.

There is no benefit to reheating the wood or epoxy, in fact there is a high potential for problems if you do so.

Again, none of this is new and all is covered in several texts and manufacture's "product user guides".

The "restored" wood, isn't restored at all. It's still the weak knee, red headed step sister to it's former self, but the surface and several mils into the surface have been soaked with epoxy, which makes it seem as if it's tougher. You'll find, under reasonable testing, very little of the physical qualities have been returned to the wood. It will be a fraction of it's former, compressive, tension, elongation, etc., strength self, though it's surface will be considerably better then the rotted mess it once was, not even remotely close to an "intact" piece.

[rwatson]

The "restored" wood, isn't restored at all. It's still the weak knee, red headed step sister to it's former self, but the surface and several mils into the surface have been soaked with epoxy, which makes it seem as if it's tougher. You'll find, under reasonable testing, very little of the physical qualities have been returned to the wood. It will be a fraction of it's former, compressive, tension, elongation, etc., strength self, though it's surface will be considerably better then the rotted mess it once was, not even remotely close to an "intact" piece.

I dont think this bit is on subject. He is not restoring rotten timber, he is strengthening soft timber.

The concept has protential for being able to utilize soft timber in higher exposure areas.

Many timbers have excellent strength, but low endurance in marine environments. This might be a usefull technique given how expensive timber is these days

[PAR]

Think of this treatment as the crust on a loaf of bread. Trust me, nothing is strengthened, it's just a surface treatment. Rap it with a knuckle and you'll find the real story, let alone give it a good swat with anything firmer then mashed potatoes.

[rwatson]

Hmm, I respect your point of view Par, but I cant see that having an incompressable, waterprooof coating on both sides of a piece of Poplar wouldnt represent a significant improvement.

Everyone knows that a coating of just epoxy will crack if banged (the loaf of bread analogy), but if he is getting 2mm of impregnation, then the timber will be contributing with its fibres to form much more than a crust. It certainly wont just sheer off the surface when the wood is bent.

But, I await further testing and evidence with interest.

[nedgrater]

Hi, Yes I agree it is just a surface treatment, but what I wanted it for was give dent resistance to new 2mm poplar strutural venner and it penetrated it completely. This is great for what I want to use it for and I am not looking for the timber to provide any real strength, (that is provided elswere).
I think this could have lots of uses though, for example, as a core material for sandwich contruction, as epoxy saturated poplar seams alot more durable than corecell or most PVC foams, and heaps cheeper too.
I have not tryed it on any thicker peices of timber yet, but because of the good results so far I think I and going to do some more experments.
I imagine different timbers will give very different results and I imagine softer wood will give better results because there is more air and possibly moisture to extract to be replaced with epoxy.
I'm just doing some experments here, I'm not saying what I'm doing is right or even good practice, I'm just grateful of the advice you have given me so far.
Thanks

[PAR]

Core materials are selected for a few basic physical attributes. Light weight, an ability to accept the epoxy bond, peel strength from it's sheathing and most importantly compressive strength, which is why balsa is so widely used.

[hoytedow]

Is it too late to go to a harder wood? Oak is harder and more open grained at comparable price. You didn't say what is the function of the piece.