Strange epoxy wetout

Yes, brushing can entrain bubbles, as can over enthusiastic stirring of resin and hardener. West System offer 3 mm foam rollers, which do a great job of applying the epoxy. Whose epoxy are you using?

Another thought! Are you using glass cloth specified for epoxy? Glass cloth used with polyester has a binder that is only soluble in solvent, which should not be present in epoxies.

Pericles

 

i,m absolutely sure that its "sagging",, ive seen that for over 20 years and its always the same reason,,your resin is "running out of the fabreic because of that stupid gravity thing. to fix wet first,, then start from bottom and work ya way up,, and put a little more "kicker" to it,, but not too much thats when ya get those tiny air bubbles in ya resin. and brushing on resin doesnt put any more air in things then rolling or anything else(apart from baggin) in fact brushing takes out more air then rolling. ive done glass work for a while, brushing (as long as not a big area) is one of the best ways to do hard areas. but the area you show,, looks like you should be using a roller. and a metal air roller to get out all the air.

 

They are some good suggestions. I can try rollers and other methods on a small spot tommorrow.
Just a couple of questions - I have never heard of Resin compatible Polyester - its all the same as far as I know. The only exception I have heard of is Balsa Core - that has to be fiddled with if you are Epoxy. I am using West Systems epoxy.
Also, what does " and put a little more "kicker" to it,, " mean please ?
I will give a report on the process over the next few days.

 

the1much

Sagging is prevented by adding fumed silica to the resin hardener mix to promote its thixotropic properties, however not too much as it's the devil to sand. Thin coats and often,wet on wet, will build film thickness and eliminate amine blush, as well as runs.

rwatson ,

Not quite sure what you mean by Resin compatible Polyester? The binder used in chopped strand mat is soluble in styrene, present in polyester resin, but not in epoxy. Therefore, be careful with your supplies of glass cloth.

Pericles

 

you could add a little thickening agent,, i dont use much epoxy,, i'm stuck in the old times and use poly or vinylester,,we use a little cabosil to thicken. i've never heard of Resin compatible Polyester , sorry.. and if its just a canoe, flop it on its side, do 1 side, let that kick off, then put back upright then do the bottom. "kicker" is your hardener, mekp for poly, doesnt epoxy have base and then ya other part (part b) is your hardener, but just a little more, hardening to fast is just as bad as not hardening at all ( so my wife says heh)

 

It's bad practice with epoxy to add extra hardener to the resin as it wastes money. With West System the ratio is 5 to 1 or 30g resin to 5g of hardener. I use pumps to get exact measurements, it's so easy - one pump of each - up to 8 of each in each batch. Polyester uses a catalyst to harden and the amount isn't so critical, I believe.

105 resin and 205 standard hardener has a pot life of around 10 minutes at 70F or 6 minutes at 80F. That's fast. See previous post 12.

Pericles

 

The more refined the epoxy (higher resin to hardener ratios) the more sensitive it is to differences in ratio. Generally, it is surprisingly tolerant of substantial mistakes, though the cured properties do suffer.

I think you're doing a few things wrong. Your over working the epoxy, using a grooved roller over cloth and using too much epoxy.

To prevent floating wetout the substrate, then let it kick (lose much of it's tack), before you apply the fabric. It will stay stuck, not lift and you can control the wetout with a squeegee, applicator, brush (they really suck and screw with the fabric placement), solid rubber or hard plastic roller. I'm a squeegee guy, as I can apply a thin, even layer, quite uniformly and not disturb the fabric.

Don't try to fill the weave, you really can't so don't bother. The next coats will do this easily, especially if you have a uniform coating method, which grooved rollers don't provided.

It's very tempting to keep working the epoxy back and forth, especially with a roller or brush. This is the easiest way to lift and move fabric, make bubbles or push uneven amounts of goo around. With practice, you'll be able to make a quick swipe with a squeegee or plastic applicator and let it go, knowing you'll have to fill the weave on subsequent coatings. The key is good wet fabric contact with the substrate. If you've worked the epoxy into a uniformly thin film, then all will appear about the same. Vacuum bagging can produce better results, in as much as resin to fabric content, but you'll still have to fill the weave afterwards.

If you're having sagging issues, you've got too much goo, floating fabric or an uneven film of epoxy during wetout. In a bright finish application, you have to work in very thin films and no thickening agents can be used. Thin uniform films don't heat up unevenly and stay within the confines of the weave, so they don't sag.

 

I had another go this morning, and I took the advice of the1Much about working it up the slope. I showed his last email to my wife
"hardening too fast is just as bad as not hardening at all (so my wife says heh)" and she agreed with that.
So anyway, she agreed to provide a bit of 'kicker' while I epoxied, since its my first boat and all, but she thought the fumes took away from the moment a bit, and said she didnt notice anything different about the hardening rate.
Anyway, I got a good result, and I will go out and check the epoxy later as well to see how it went off.
I remembered reading how extra hardener didnt help with epoxy, but I did experiment with adding a bit of the fast 105 hardner to the mix to see if it helped avoid runs.
I also tried 'wet' on 'wet' application (we are back onto the boat topic now gentlemen) and other than having to wait around till the base coat was tacky, that method seemed to provide good results.
Back to the original observation, the thorough wetting out with a squeegee gave a more uniform transparency, but still not totally successfull, You can roll and squeegee over a section, and there will still be some visible bits and some almost transparent bits. in that section.
If 4 oz clother goes transparent, maybe I am just seeing an effect of the weave. Obviously the fibre thickness and mechanics of assembling the cloth are not a precise science, so maybe its just a function of varying cloth specifications.

 

You can get the West System "How to" DVD from HQ. Catalogue number 002-898.

Pericles

 

I can't tell you enough about how foolish it is to "add more kicker" to epoxy. This material in not a catalyzed product, it is an activated material and addition hardener can actual dramatically affect the strength of the laminate, including the bond (which may or may not take place). It's also irresponsible to suggest such for epoxy use, particularly to folks that are novice applicators. Having to scrape off uncured cloth and goo, because of this type of advise is just wrong.

Mixing different hardeners into resin is also a very bad idea, especially if the ratios are not the same. Even though the can of hardener may look the same, you have to check its content by volume (printed right on the can) and even this doesn't insure compatibility with the other hardener.

Again, only 4 ounce (or less) will become completely transparent. All other heavier weights will show a weave. Even 4 ounce will show a weave with the first applications of epoxy, but subsequent coats will hide this completely. Ideally you want the weave to show, uniformly all over the surface after the first coat. Of course, milky areas need addressing, but if the weave is showing and it's looking completely wet, then that's it, time to stop and wait for the "green stage" and another coat, which will begin the process of filling the remaining weave.

105 is West System's resin, there is no "fast 105", They do have a 205 (standard hardener), 206 (slower hardener), 207 (special clear coat hardener) and 209 (very slow hardener).

Almost all epoxy effort is reliant on user experience. It takes considerable time, before you can achieve near perfect results with the single swipe of a squeegee.

 

I just had to step in here. I have three boys, 2 in middle school, and one just into college. Sometimes it is difficult to get them to listen to sound advise. In part do to the foolishness of youth, but also partly do to the fact that there is a lot of advise coming from different sources. In this case I would consider the source(s) of information. Par and Pericles have both given solid reliable info that can be verified. It is obvious that Par has had much experience with epoxy; you would do well to pay careful attention to every word that he has written.

Now to verify your sources of info, compare how close what has been said to these instructions from the West Systems User Manual:

 

Par, Pericles and MOB (Tom) have offered some good advice here and I will not rehash what they have said.
In tighter weave fabrics, it can sometimes be difficult to get air out from underneath the cloth when wetting out from the top. When I had inexperienced people working with these cloths, I found they would trap a lot less air and get a better wet-out with the following process:
- Wait for previous coat (in your case the saturating-the-wood coat) to start to kick.
- Spread a thin layer of fresh resin on top of it, about 1/2 to 2/3 of what you'll need to wet out the new layer.
- Place the cloth and get it smooth, but do NOT apply any new resin, and work only with dry (not resin-covered) plastic spreaders/squeegees
- Once the cloth is worked smoothly into the resin and has soaked up as much as it can (give it 5-10 minutes with minimal working), spread only just enough resin on to fill the weave, do not try for a smooth surface
- If a smooth surface is needed, fair it later
This process worked well and yielded virtually perfect wet-out on several layers of a pair of irregularly shaped moulds, with only about 20% of the crew having had significant experience. The moulds we did this on had an epoxy foam core that, left to its own devices, soaked up resin even worse than wood does.

So try making sure you are getting enough resin under the cloth- air pockets can get out through dry cloth but once you plaster new resin overtop, they are trapped within the fibre bundles.

And, as has been emphasized already: NEVER screw around with epoxy's mix ratio.

 

um,,, i think i made it clear i didnt use much epoxy, and my experience was with other "stuff", then above me im pretty sure pericles and you(par) told him it wasnt coolz, i was jus tryin to help him guess it out because he was gonna try again whether he got responses or not. and by toms response we can see that epoxy has a "fast" and "slow" hardener, which im just guessing that its same stuff jus faster"ratio of catalyst higher", but sorry ta get everyones dungerees floppin heh
and i still say no matter what material is being used,,its (rwatsons problem) 100% caused by sagging i just didnt know how to prevent it in epoxy
so now with this info,, i would suggest,,,use the fast hardener

 

Pretty Normal

RWatson

What you are seeing is normal. I have seen this in all the boats I have worked on and later on there seem to be no issues. Glass in fibres is still visible when wet. I have seen but not really thought about the effect you observe where the site you dump the epoxy on goes clearer than the surrounds.

Maybe it is something to do with dumping lots of resin rather than a thin layer which has some air entrapped. I always use a squeegee and find that the resin I have worked in looks a little creamy as I work it. This is obviously air mixed in with the epoxy from working it around. Don't worry about these tiny air bubbles as you work almost all of them out of the resin and those that stay in are normal and boats have been built with them for years.

As others have said never play around with epoxy ratios. Epoxy is not precatalysed like polyester resin. Polyester will go off if you leave it long enough as it has all the components in it to link the small chains together and go solid. Epoxy on the other hand has a part a and part b. Part A is a major part of the chain and part b is the missing link for the chain. Every single part A needs a part b and adding extra does nothing but make the epoxy weaker.

If you want to get the resin to go off faster of to make it thinner make small batches and heat them up. Think heat not hardener when trying to manipulate epoxy.

cheers

Phil Thompson

 

Discovery Time !!!

Had a sit down today and read a West System user Manual - again!
Looks like my puzzle is solved -
Which Hardeners are best for clear work? Not the ones I have been using.
The ONLY hardener that does not have the words "Not Intended for Clear Coating" is the 207 Special hardener (3:1 ratio)
A local wooden boat magazine had a couple of articles about this hardener recently, and titles the article "Wests best kept secret". It sure is!!!
ALSO - In a sidebar is a section titled "Clear Wood Finishes". It actually suggests that the epoxy is to be laid on top and allowed to saturate the cloth - and not force it with brushing or spreaders, to "avoid trapping air in the fabric"
I will attempt to get some 207 hardener over the next few days and see if I can observe a difference.

For all the comments about the techniques and hints added to this forum, it seems like a lot of people havn't noticed these small details in the literature either - it will be intersting to see the difference in the results.