View Full Version : thinning epoxy with acetone
07-25-2004, 09:09 PM
I am building the millcreek 13 kayak from clc boats. I have gotten to the point where all my panels are cut and wire tied together. Last night I started to fillet and tape the inside bow section. I am using system 3 epoxy with a medium hardner and it starts to set up to quick in the mixing cup which causes me to try and rush as to not waste it. Will purchase the slow hardner to solve this problem. Now, the second problem is that I am using 3" wide 9oz cloth tape for the seams and is a little more difficult to wet out than I thought. Can it be thinned out a little with some acetone or styrene to get it to wet out the cloth a little easier without sacrificing any strength ? Luckily it was only a small section of the bow inside and I can fix it but any advice on thinning and maybe a mix ratio of epoxy to thinner would be helpful.
07-25-2004, 09:38 PM
Unless you REALLY know your epoxy chemistry, thinning the stuff you're using to tape your boat together is most likely going to be a huge mistake which will come back to haunt you later, if it doesn't do it during the application process itself. Last time I checked, there wasn't any styrene in any formula of epoxy that I know of. It's extremely flamable and sometimes used to dilute surfacing agents, etc. on polyester resin, but I've never heard of anyone adding it to epoxy. Acetone is a solvent, but often not good as a thinner, so I have serious doubts about the structural quality of the epoxy/fiberglass once diluted with it.
Best approach is to get hold of the proper resin and hardener to do the job and do it right the first time. Three inch tape should be fairly quick and simple to apply. If need be, mix smaller amounts as you go and work small sections. It's quite feasable and possible to glass an entire boat in one shot using fast hardener mixed in small batches as you go, so 3" tape should be a snap with the right resin and a little practice.
07-25-2004, 09:49 PM
I'll second what Todd said...
07-25-2004, 10:57 PM
As I understand it, the solvent does not chemically bond with the epoxy, but is within it when it cures. Later, it finds its way out and evaporates. The spaces in the epoxy where the solvent was is empty. Result: The remaining epoxy is a 'sponge' with greatly reduced strength and greatly increased permeability.
07-26-2004, 12:17 AM
I agree with the rest. Now let's get the tape wetted out a little faster.
Lay a piece of visqueen on the top of some plywood which is sitting on some sawhorses.
Have your strips of glass cut to size and layed out so you know where each one goes.
Wet the glass by pouring some resign on them and use a squeege to work it in and squeege out the excess.
then pick each piece up and lay it where it's supposed to go.
This will do 2 things.
1] It will get the resign out of the cup quicker and spread thin so that it doesn't exotherm as fast.
2] You will not have excess resign puddeling in the boat and make excess weight.
07-26-2004, 07:42 AM
Hey, Norwood Eastie, here are some thoughts, experiences. I thin epoxy, per my mfr's instructions, only when applying to wood that is probably too rich in oils (such as teak). For this thinning I use no more than 5% denatured alcohol. It lets the epoxy, supposedly, soak into the wood -- becoming keyed in and is the first coat, followed by ususal coatings for the intended use. The thinning really has nothing to do with extending the time before the epoxy kicks in. To extend the kick-in time you've got to have the slow hardener, and you can further extend kick-in time by de-massing your mixed epoxy -- pour in into a pan, or by dumping it directly onto those glass tapes.
Unless working on a "ceiling" surface (fun!), my usual way to work is to not presoak the tape, but to lay it on the surface and brush the epoxy on to it, with the wood surface "ready" -- roughened up, wetted, whatever is right for your procedures. (A series of coats of epoxy on the wood prior to the taping is -- what does CLC say? -- probably needed and if its been more than 24 hrs. after application, then rough sanding too....). Good luck.
07-26-2004, 07:46 AM
Oh, and acetone=BAD NEWS 4 U, denatured alcohol = LESS BAD NEWS 4 U. Avoid using acetone if you can--seek alternatives, otherwise dress like an astronaut waddling around on the moon.
07-26-2004, 10:22 AM
What manufacturer, Billy? Surely not System Three, WEST or MAS, the only ones I've used on boats.
Use slow hardener, work faster, or in a pinch put the mixed batch in the freezer (No SWMBO, it will not poison the family) to slow things down a bit. You can use a frozen epoxy laden brush tomorrow as well.
07-26-2004, 10:39 AM
Others have given you good advice (don't use acetone to thin epoxy).
System 3 works quite well with glass fabric. You should not have to thin it. Try this method for taping seams:
Use small batches. You can pre-measure cups of resin and hardener and line them up. Just mix up the next small quantity as you need it. This will allow you plenty of working time with each batch.
Put the epoxy on the wood first. Lay the fabric in place and use a plastic squeege to smooth it down. Work the wrinkles out on the bias of the fabric (45 degrees to the thread direction).
After the epoxy cures to rubbery state and before it gets hard, use the curved blade from a Stanley Sureform to slice away any high spots or drips.
Before the epoxy cures all the way, recoat to fill the weave of the fabric.
[ 07-26-2004, 10:41 AM: Message edited by: bainbridgeisland ]
07-26-2004, 12:58 PM
Thinning epoxy=bad news. To get a little more working time,put it in a shallow container after mixing, this builds heat slower than a small mixing cup. I have been known to keep my resin on ice to extend working time!
[ 07-26-2004, 01:00 PM: Message edited by: Bob Adams ]
The System III slow hardener will give you all the time you need for just about any task. I use epoxy in well over 90 degrees and hardley ever use just the slow hardener by itself, usually a mixture of #2 and #3.
07-26-2004, 01:30 PM
Standard S3 epoxy should be plenty thin for laminating. We stock the new S3 silver tip resin, which they make especially for lamination. Its viscosity is listed at 900 cps (thinner than the standard resin) - its also stronger and has a much better pot life. Silvertip is also clear and zero blush.
No matter what, I would recommend a slow hardener this time of year.
07-26-2004, 02:30 PM
Thinning the resin with acetone its not a good idea, in simple words it just ruins all the resin qualities and strenght, someone uses the acetone on hardened (sandable but not completely cured) epoxy to re-soften it and get a better bond with a successive resin application, but even this isnt the best practice. If you want to use acetone use it to clean the utensils from the resin, in the open. You can use a squeege to force the resin everywhere, like the others suggested, or even a metal roller of really irregular surface (bumps or grooves) this forces the cloth to absorb the resin sort of like you would do squeezin a sponge in the water.
For little areas brushing generous resin directly on the surface and then applying the cloth, followed by rolling, or with the squeege its everything the cloth needs, the other resin coats will take care of the weave.
The cloth has to be wet to become pratically transparent, white areas are too dry, tapping on them with the brush tip can be enough to wet them, white spots of dry cloth wont get "wet" with the next coat unless there has been no resin at all in them (and in that case they still wont wet at the edges). Any quantity of resin other than the minimum needed to have a transparent cloth its simply too much for just one coat.
The resin pratically start curing as soon you mix it with the hardener, generating some heat itself, and the warmer the air the faster the curing is, to slow it down use flat and wide containers (as Bob said)instead than bowls, cans, or plastic bottles, the ice to cool it down works well too but dont lower the temperature under the minimum the manufacturer requires, and not for long time (if you have the possibility one useful thing is a pan inside a bigger pan connected to an hose and having cold water running in between the two all the time).
If the resin and slow hardener mix still hardens too much to be workable (honey thick) then you need to use smaller batches (if it gets lumpy then you didnt mix it well enough).
[ 07-26-2004, 02:41 PM: Message edited by: Corso ]
07-26-2004, 08:38 PM
Hiya, Norm. The epoxy I use is RAKA, LARRY is the majordomo, and he sez that denatured alcohol (5% max.) thins the epoxy mix for penetration into oily woods. Prior to this epoxy soak coating, BTW, is a wiping of the wood with denatured alcohol to rid the wood's surface of oil. Follow the thinned epoxy (penetrating coat) with regular epoxy, and/or with thickened goop or whatever you have in mind. I've done this a great number of times; it works...so far. Indeed, today, I was shaping the cuddy trunk's nose made of 3 blocks of rosewood (not as oily as teak) -- each held to the others and to the rosewood trunk sides with this process.
Earlier (years earlier) he called for acetone as the wiper, but has changed on that one.
Are we thinking differently?
07-27-2004, 09:11 AM
I've had good luck with the medium speed hardener that gets mixed in the plastic cup, and then placed in an aluminum pie tin, it seems to slow down the reaction a bit. Keep the tins in the freezer, and have your wife run them out to you as needed. I rarely go for more than three squirts of hardner & resin at a time (West System), that's a pretty small batch, but enough to get some work done (a helper is great for the mixing with such small batches). When I roll it on, I use a bigger pie tin.
07-27-2004, 09:37 AM
Thanks, Billy. No, I don't think we are thinking differently, just coming at the problem with different preconcieved misconception. ;) I've not used RAKA nor talked to their technical people so I would not presume to disagree. Wiping down is not in contention. I do have the impression from a WEST Epoxyworks publication report that their epoxy become less and less water resistant as it is diluted and from a conversation with Kern Hendrickson at System Three, years ago, that dilution does not enhance penetration. The Chemist disagreed with Kern with regard to CPES so I'm now conflicted. Flip a coin or stay with the guy with a real name? Kinda makes one's head hurt doesn't it?
07-27-2004, 09:56 AM
Mix up a bit of epoxy and brush a bit of it on to a piece of wax paper. Now add some solvent to the epoxy (acetone, or any of the solvents) and brush some on to the wax paper. Let the samples cure a few days then peel them off the wax paper and check them out. You'll see first hand what sovlents do to epoxies.
For longer pot life try keeping your epoxy cool by placing your epoxy batch in a pan of ice water - thus lowering the temp. Also, smaller batches and shallower pans with more surface area will all extend potlife. Finally you might try an epoxy thickener that stirs in quicker and easier (compared to fumed silica as an example).
progressive epoxy polymers
07-27-2004, 10:08 AM
Right, Norm. Confusion reigns in the zone of multiple brands of differently whipped up epoxy systems. Maybe if Nader ever gets the boating virus he'll have Consumer's Report do a comparative study. (No political responses, please!) Wouldn't that be informative? Everything from cost to coverage to bonding to strength? Wow.
The RAKA stuff, economic to be sure, is pretty fluid so when the denatured alcohol is yet added to it the result is almost like water. Larry (RAKA's owner)sees this stuff, I guess, as penetrating enough into the pores of de-oiled oily woods so that it'll form a coating/dam of sorts and a base for regular epoxy to build on. As mentioned, it has been working for me on both teak and rosewood. Obviously a chemical bond is needed so the 2nd coating is within 24 hours. I first did this in the fall of 2000 for an outer stem (about 6 or more pieces of rosewood) which has been varnished and seeing weather all this time with no indication of any delamination.
For those limited to 3 squirt applications, might I mention that I sometimes work up to 6 squirts (RAKA is a 1:2 mix, the 2 being the resin), using the fast stuff, in the summer. I do this when I'm rolling the epoxy onto raw plywood or onto xynole cloth. I dribble it out, roll it some, dribble...roll, dribble, etc. The objective is to get lots out and down but to get it the heck out of the (yogurt) container durned fast. I follow up with evening out the dribbles with the roller. For thickened goop as in fillets, etc., caution, slowness of application usually indicates the slow hardener and a maximum of 4 to 5 squirts with a need to demass along the sides of the yogurt container.
08-02-2004, 12:08 PM
Just received a reply from Larry at RAKA epoxy concerning thinning. Here is what he had to say about his previous instructions for epoxying teak and rosewood:
Thinning is not normally recommended and can give the negative qualities you suggest but gluing difficult hardwoods is a special situation and you are only using it for you first penetration coat.
So, given the earlier back-and-forth on thinning, I'll continue to do it simply to get a hook into oily woods, but only for that purpose. My experience with the thinning has been just with the mentioned woods. I have no idea how thinning is with other woods.
Yesterday I ran a lamination of 3 layrs of rosewood through the bandsaw. It had been epoxied using the thinning as a first, penetrating coat and this was followed with one coat of regular epoxy thickened with fumed silica. This was done some 3 years ago. The epoxy lines looked fine. No Swiss cheese seen, and it's nearly lunch time!
08-02-2004, 01:37 PM
IMHO You should give it a try. It's your epoxy, so thin it if you want to! ;) I had a similar question recently and got lots of expert opinion. After I digested the opinions I did some experimentation. I found that for what I was doing, coating marine mahogany plywood, no glass, that the thinned epoxy worked great and gave me the finish I wanted. I thinned it about 20% with Acetone. I also use acetone as a wipe before painting, varnishing, or epoxying. It's wonderfull stuff and evaporates quickly. Wear gloves, stand upwind, and read the MSDS. It's best not to smoke while using it :D . Goodluck.
I built a MC13. Wetting out 9oz tape shouldn't be a problem unless you're trying to do this in 45degree temps. Methinks it's too hot for the epoxy you are using for your familiarity with the materials. Acetone evaporates VERY QUICKLY,,and tends to take apart some kinds of gloves/barrier protections. If you're new to all this it doesn't make sense to increase your exposure to epoxy by introducing an extremely volatile solvent that will make a less than optimum bond for an essential part of the structure in the kayak.
08-02-2004, 02:13 PM
"Thinning is not normally recommended and can give the negative qualities you suggest but gluing difficult hardwoods is a special situation and you are only using it for you first penetration coat."
I can accept that and wrap my preconcieved misconceptions around the process. Kern Hindrickson (Hinderson? Seems I can't his last name for sure) at System Three told me once (i.e. I understood him to say) that the solvent penetrates but the epoxy does not necessarily follow. The Chemist took great exception to Kern's comments as I related them. So there I was, caught in the middle, I tended to tilt toward Kern since I know who is is and where he is coming from.
I also tended to generalize a bit from WEST's report on the effectiveness of diluted epoxy to prevent water intrustion. Upon reflection it seems there would be a continum from paint on raw wood to paint on undiluted epoxy. The paint will protect the epoxy so does it matter if it is diluted or not?
Ah, it just makes my head hurt. The only thing I know for sure is the temp out side is far on the wrong side of 90 so I'm taking the grand neighbors and going to a movie this afternoon. Keep your epoxy batches small and dispursed. tongue.gif
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