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View Full Version : Epoxy Removal Hell: Tips and Tricks?



kevinwal
02-16-2002, 10:19 PM
I'm just about half-through removing gobs of hardened epoxy from the interior of the hull, using a hair dryer to soften the stuff and a chisel to hack it out. This part of the job seems to be talked about very little, yet I'm spending so much time on it! Anybody have any little tricks or tips in their toolkit? My wife suggests I use "paint thinner or something." smile.gif

Kevin

capt jake
02-16-2002, 10:20 PM
Mask, Mask Mask. Sorry about your plight.

dasboat
02-16-2002, 10:32 PM
A heat gun will be faster.But,if you don't have one a dryer is fine.

NormMessinger
02-16-2002, 11:00 PM
No No. Not paint thinner. It wont affect epoxy. Heat perhaps. I rely on brut strenth and awkwardness, which is to say sand paper. Remember wood is soft, epoxy is hard and think aerobically.

Good luck and best wishes.

--Norm

Don Maurer
02-16-2002, 11:42 PM
A heat gun and scraper is the best way I have found to remove globs of epoxy once it has cured. I try to clean things up as best I can with acetone after the epoxy has started to kick off to keep scraping to a minimum.

MikeP
02-16-2002, 11:51 PM
I tried the heat and the scrapers, but what worked well for me was the Dremel roto tool with the 1-1/4" fiberglass reinforced cutoff wheel. It is the only fiberglass I've used on my boat so far! This is dusty but fast. Use a mask and have the shop vac handy. :rolleyes:

M

kevinwal
02-17-2002, 12:02 AM
You're a better man than I, I've tried to use my Dremel tool, and have found it almost impossible to control. Heat and scraping seems to be by far the fastest method I've discovered, so I guess I'll hang with it. The paint thinner thing was my wife's idea, I never seriously entertained it, but it does demonstrate her manifestation of the "surely there must be a better, a *modern* way" attitude that I also had going into this thing. I guess sometimes there just isn't a better way. Thanks!

MikeP
02-17-2002, 12:26 AM
Kevin,

The Dremel tool may fit in one hand But I have to use both hands to control the angle of attack. With the cut off wheel (#426) at about 15,000 rpm, there is very little heat build up and one can take the epoxy down to the point where light touchup sanding will level it.

I didn't mask my plywood lapstrake construction and when I turned the hull over I had to become an expert on removing the hard gouge blobs from all the lap joints. :mad: I was able to do a section a night.

Good Luck,
M.

stan v
02-17-2002, 08:39 AM
Can you get a grinder to it? If so, hook a vac, and commence. 80 grit, or coarser

ken mcclure
02-17-2002, 08:59 AM
Wipe on, Chisel off. Wipe on, Chisel off. It's a Zen thing. Get into the groove and use the time for deep thinking. :cool: Heat gun is it.

IanW.
02-17-2002, 09:18 AM
I've been trying to remove epoxy from boatbuilding for years. Little luck so far. Their PR budget is bigger than mine.

IanW. ;) ;) ;)

bainbridgeisland
02-17-2002, 11:48 AM
I know it is tempting to use heat to remove blobs of epoxy but this may not be the best way. Turns out, epoxy is very sensitive to heat. You could easily damage the boat by using too much heat. Even if you don't damage the boat the extra heat may be post curing the adjacent blobs making them harder to remove later.

There is not a specific temperature threshold that will cause all epoxies to be damaged. The threshold varies with each particular epoxy compound. Some epoxies used for boatbuilding would be permanently damaged starting around 250 degrees F. Thus while you are cleaning the blob off, you may be damaging the surrounding epoxy as well.

Here are some ideas about cleaning off epoxy in order of preference. Clean the epoxy off before it cures. Mask off areas likely to be inaccessible before applying epoxy. Clean the epoxy off as soon as you can after it starts to cure (the day after is far better than a week after). Use a chisel and cabinet scrapper on partially or fully cured epoxy. A plane will slice off blobs too. Sand or grind off the blob.

At the boatshop I used to work for, we used a slow speed disk sander with a feathering disk (80 grit sandpaper) to smooth up the inside of glued cedar hulls. This was followed by a DA with 120 grit and then orbital sanders with 180 grit.

Personally, I would never use the heat gun. It is too risky.

kevinwal
02-17-2002, 12:55 PM
Can you describe what you mean by damage? Is there a risk that the planks will spring free at some point in the future? I've finished half the interior of the hull using a hair dryer, so now I'm quite paranoid about proceeding with that method, even as I dread tackling the other side without it. Thanks!

Kevin

PierreP
02-17-2002, 12:59 PM
Try paint remover!

Actually I did'nt try it myself yet, but this technique is described at some point in the book How to build the cosine wherry. They use it to remove excess epoxy using a scraper when the strips have been sealed with a thickened epoxy mixture.

I would make a test on a scrap before...

bainbridgeisland
02-17-2002, 04:52 PM
[QUOTE]Originally posted by kevinwal:
[QB]Can you describe what you mean by damage?

Damage means the epoxy is less strong than full cure. How much less depends on how sensitive the epoxy is to heat and how much heat it absorbed. Another consequence of heating up the epoxy is that it becomes more rigid (more brittle). Thus it becomes less damage tolerant and more sensitive to peel loads in a gluing application. Beyond these considerations, I don't know. I have seen very little testing of epoxies that were heat damaged. Much work has been done up to the glass transition temperature (Tg), but after that, very little.

"Is there a risk that the planks will spring free at some point in the future?"

Probably not, but it depends on how damaged the glue is and how the glue joint is loaded.

Glue joint loading: All glues work best when loaded in a combination of compression and shear. Press your hands together and rub them real hard for an example of compression and shear. Glue does not work well for peel loads. This load is like peeling a piece of tape off a surface. Now, if you are building a lapstrake or strip plank boat with few transverse frames, the glue joints could develop considerable peel loads. More frames allow less peel load and the glue joint will be less affected by brittle glue.

Amount of damage: It is hard to judge the amount of damage. For tight joints in lapstrake and strip planking, the wood will have insulated most of the joint from excess heat. Thus only the glue near the surface would be damaged due to heat alone. However, the glue will go through a transition of brittle weak material to brittle strong material to the normal, damage tolerant, resilient strong material.

This is about the worst geometry imaginable for a glue joint. The edges of the timber naturally create a stress concentration that would line up precisely with the brittle weak material. Even if the glue joint never actually broke, chances are micro-cracks will develop around the highly loaded edge of the joint. The micro cracks will permit water intrusion.

Another problem is damage due to moisture trapped within the epoxy. All epoxies absorb some moisture. After the epoxy is heated to 212 degrees F, the moisture becomes steam and expands. The expanding steam will damage the epoxy. By the way, expanding steam trapped inside of wood will also cause damage. Wood is a good insulator though, so I would expect damage to be concentrated near the surface. How much epoxy damage due to steam? Again, I don't know the answer since it depends on so many unknown variables.

I certainly would not recommend using heat at all. You can make a valid argument that as long as temperature stays less than Tg damage will not occur. However, you would still be post curing the epoxy, making it more brittle and less damage tolerant at the edge of the glue joint.

Rich VanValkenburg
02-17-2002, 09:41 PM
I've used paint remover on hardened epoxy. I let it sit there awhile, just like with varnish, and then used a sharp ProPrep scraper with mild pressure. It takes several coats of remover, but it works. I used the Sears non-explosive stuff.

capt jake
02-17-2002, 09:53 PM
WOW!bainbridgeisland makes a very convincing arguement! I will keep all of this in mind on the 'next' boat.
Happy 'scraping'?? :D

John B
02-17-2002, 10:02 PM
Thats because BainbridgeIsland knows what he is talking about. It certainly makes me feel that my " clean it up before it sets "policy is worth keeping, or as my granny used to say " a stitch in time.....

capt jake
02-17-2002, 10:10 PM
Does this bring us to my original post, "MASK, MASK, MASK?" Sorry, I borrowed that from another site (he won't mind)! smile.gif But in the mean while, scrape, scrape, scape! :D
Good luck. smile.gif

Don Maurer
02-17-2002, 10:43 PM
The trick to using a heat gun is to keep it moving and to scrape while you are heating. As soon as the epoxy gets soft enough to start coming off in thick scrapings, remove the heat source. What Bainbridgeisland says is probably true, but there is no need to apply that much heat to soften the epoxy. Again, the less time it has to cure, the easier it is to remove. I try to do it the next day.

Wild Wassa
02-18-2002, 12:26 AM
Kevin, Keeping the chisels very sharp helps. Do not hit the chisel. Gently but quickly, shave the offenders 'off', no hard thumps. Lots of light strokes and attack the problems from different angles (if possible). Shave 'up the ramp not onto a step'. With a very low heat (luke warm in a warm workshop), the chisel might bite that little bit sooner, or dip the edge of the chisel that will work .

Masking the surrounding area with light foil will take the sting out of unavoidable heat gunning. Test well Skipper!

The grinder is the time saver. After the second or third, 'shock-horror-shock', Welcome GRINDERMEISTER!

Author's Special Note: Thank you for your most generous Contribution(s) Mr Bainbridgeisland. I find them just exceptional for their detail, accuracy and penmanship, not to mention the 'benifits' that we all gain. My thoroughbred has stopped galloping thanks to you, Bravo. I thought I was being tracked by an Akula Class.

Warren.

JJoohhnn
02-18-2002, 01:39 AM
Hi kevinwal:
When ever I work with epoxy, I try and clean up any blobs while they are still wet by scraping them up with a metal 2inch wide or so putty knife. This excess epoxy I use to fill knots and other imperfections in the plywood I use, so no waste.
If however I do have the odd blob of epoxy to deal with, I use a wood file on it...takes that blob out in no time flat and with minimal effort.
Hope this helps....It has worked great for me :cool:
Regard John

Paul Brooks
02-18-2002, 04:23 AM
Mask, Mask, Mask - I assume you mean with tape. But which one. When I've tried that (with plastic packing tape), it left an awful mess as the epoxy seemed to bond :eek: with the tape glue - it still had to be all sanded off. BTW I used a Makita palm sander, which I found very effective (and, I have to admit, a small belt sander (2in wide) - I know it was wrong, but... :eek:

Best regards
Paul

ken mcclure
02-18-2002, 08:38 AM
Check with your epoxy manufacturer regarding heating and post-curing. I seem to remember reading a thread awhile back that talked about this very thing, and it was mentioned that the heat would not harm the specific epoxy being discussed. I'd be willing to bet the answer differs for each manufacturer.

Where is chemist when we need him? For that matter, where IS chemist, anyway?

PierreP
02-18-2002, 09:11 AM
That's right Joohhnn I worked a lot with epoxy glass and carbon and THE ONLY good tool to work it after cure is a wood file. Try it.

But it may not be easy to work inside the hull and in tight corners. Also hold it firm to avoid catching the wood...

JJoohhnn
02-18-2002, 09:58 AM
Re masking tape:
Whenever I somehow leave masking tape on the surface for too long and glue residue stays behind on the surface after I pull off the tape , I use paint thinner and a rag to rub it off...Comes right off...
Regards John

Wild Wassa
02-18-2002, 10:24 AM
Paul, Tape residue is easily removed with a soft white acrylic eraser. All tapes leave a residue. Fine quality painter's tapes are the ones to use. Do tests to determine the best time to remove tape. Masking for a painted 'hard edge' requires pulling the tape immediately compaired to masking Epoxy which can take up to 24hrs depending on the the ambient temperature. The longer the tape is left on, the harder it is to remove. Do not let the tape get wet, from dew overnight, it will 'STICK' even in warm weather. Keep the tape clean! Do not let the tape edges pick up dust, from rolling around the shed. This will result in a painted soft edge. Put the tapes in their own plactic zip-lock bags immediately after use.

I do use a lot of painter's tape, both plastic and paper based. Standard sizes of 3cm and 8cm, medium stick and light stick only. I like 3M's blue 'medium stick' paper based tape best, it is strong and leaves little glue residue - mostly. At which angle do you pull the tape off?Parallel to the surface and back over itself? No one way seems best for all media.

Warren

[ 02-20-2002, 06:42 PM: Message edited by: Wild Wassa ]

TomRobb
02-18-2002, 10:41 AM
If one is faces w/ a recalcitrant blob might a soldering iron tip be more surgical in its heat application? Touch/scrape - touch/scrape, etc.

kevinwal
02-18-2002, 12:03 PM
This is all really great information, and I appreciate everyone's input. Recall that this expoy nightmare was born by way of the planking process for an 8' Acorn dinghy of plywood lapstrake construction, and I'm curious about the masking techniques you all have employed in similar circumstances.

The building frame and forms are a real obstacle to getting at the tape so soon after epoxying. I guess I could imagine masking between the forms, leaving a small gap at the form edges, to be cleaned later on, which would certainly reduce the amount of work.

Thanks again,

Kevin

kevinwal
02-18-2002, 12:07 PM
Yep, a very sharp chisel is an absolute must. I find that I need to stop and sharpen the chisel after about 4 feet of glue removal. Amazing.

Also, I'm using a hair dryer, not a heat gun. Anybody know the temperatures such a thing might generate? When I was an electronics type, I used a heat gun, which we used to use to light our cigarettes. I'm actually quite fearful of using any kind of machine on this boat owing to its 1/4" planking. One slip and I've got a nice hole in the side.

Kevin

Kristian
02-19-2002, 12:13 AM
I take it there is no chemical solution to remelting epoxy.

ford
02-19-2002, 07:30 AM
I have found that good old metho works great on uncured epoxy. On cured epoxy a sharp chisel very carefully and finish of with a Feine Multimaster with a 120 grit, an excellent tool

Will
02-19-2002, 11:24 AM
I think the builder John Brooks , who wrote an article in WB on glued lap construction , has the sensible solution : duck under and wipe off each seam as you proceed . He sets up his molds in a way that facilitates this .

Two parralell boards running the length of the boat form the base of the setup ,but there aren't rungs or cross spalls at every mould . Instead there is a third lumber longitudinal right under the keel of the inverted boat , like the ridge of a house . The moulds are ridgidly attached to this with long screws . The wide boards have a plumb cut just like rafters , with the shape of the boat sawn on their outside edge .

The bottom parrallels are attached with cross pieces every 4 feet or so ,but there's plenty of room to work between them and duck under as you work your way along the seam , creating the finished profile by carefully striking off the fresh epoxy . I'm suprised if people are simply letting the excess run thru and harden , to be delt with later . This seems inelegant ,and worse ; not fun .

I like rasps , as mentioned , for the inevitable isolated lumps ,and riffilers ( small shaped rasps ) for tight spots . I like to finish off the lump with a handheld scraper blade . It's faster than hand sanding .I also like the hand scraper for those sad sags or runs that can develope on vertical coated surfaces after I've left the shop .

[ 02-19-2002, 11:28 AM: Message edited by: Will ]

Ross Faneuf
02-19-2002, 01:36 PM
Let me second everything BainbridgeIsland says.

I would never use any kind of heat on epoxy - it's worst property in my opinion is that it degrades at temperatures > 150 Fahrenheit or so.

It's too late for this job, of course, but masking and removal of drips, blobs and squeezle (that's the technical term for the excess squeezed out of a joint smile.gif ) is most important; you would not credit how much easier it is to remove uncured epoxy than cured - even when it is beginning to go off. I often make up a scraper by sharpening a stir stick at an angle; does a great job of cleaning up seams. Any kind of putty knife works; they can be cleaner with denatured alcohol. After scraping, you can also wipe off the last bit of squeezle or excess by rubbing with a sturdy paper towel (e.g. Scott Rags in a Box); denatured alchohol also will remove fresh epoxy and can be used to clean tools. While not actually a solvent for epoxy, it works quite well.

If you're using epoxy for joinery, it's entirely possible to clean up so well using the scrape/rub/rub with alcohol sequence that you will need only a light sanding (as per usual) before finishing - even finishing bright.

For hardened epoxy: planes work fairly well, though they dull quickly. A compass plane is a big help on interior curves. 60 grit in a grinder or random orbital sander works, though slowly, and tends to reshape the surface in ways you may not like.

Other useful hand tools are 2nd cut wood rasps, particularly for edges. Stanley surform works very well, and is what I typically use to remove the worst of big drips, blobs, or squeezles. You can make your own compass plane by bending one over a piece of wood cut to the right radius. They make this little curved face surform with a blade only about 2"x2", which is really good for interior curved surfaces. Surforms dull fairly quickly, after which they're useless. I've found a lot of variation in sharpness as they emerge from the shrink wrap, with some being almost useless from the getgo.

I rarely use chisels on epoxy for these reasons; they tend to chip away the stuff, rather than cut it, and it's fairly easy to get into the surface you're trying to clean, or chip bits out of it (rather like the problems of cleaning up bungs with a chisel). It's also fairly easy to knick or chip the chisel's edge as well - I have some very very good chisels that I've accidentally cut a few bronze screws with, but which have suffered more damage from epoxy - in this case, my usual System 3 mix with silica filler.

3M blue long-mask is my favorite for masking for epoxy. However you use it, or whatever tape you use, you'll probably have to cut through the epoxy at the tape edge to get everything to release. An example of something that's worked well for me is sheathing the bottom of a dinghy with Dynel and epoxy, although the technique works well for other things. (1) mask the line which separates expoxy or epoxy/cloth layup. (2) Layup or coat (3) monitor the job and wait for the 'green' phase of the epoxy. In this state, it is partially set up; has lost all or virtually all of its stickiness; but is still somewhat rubbery or very plastic. At this moment you can cut it by hand with a contractor's knife (box knife), including any cloth. Follow the separation line by hand, changing blades as the gum up or get dull. Peel the tape immediately (green epoxy will often release from the tape anyway at this point). Unlike paint, peeling the tape will NOT break through epoxy, which is both thicker and much stronger. BTW make sure the tape is well rubbed down, or the epoxy will find its way under the tape and make the whole job MUCH more difficult.

Epoxies will sand well as long as they are properly formulated and well cured, and you use good quality sandpaper. My favorite is 3M gold, but Norton and the various German manufacturers are also good. Porter Cable is OK, but not as long lasting, and both the paper and adhesive (I use PSA) tend to wimp out in hot humid weather.

I use epoxy filler as bungs rather a lot, especially when I'm working with plywood faced with epoxy with or without fiberglass. To avoid chipping, I clean these up with a rasp, then sand flat. Completely invisible when well done.

[ 02-19-2002, 01:42 PM: Message edited by: Ross Faneuf ]

Wild Wassa
02-19-2002, 04:53 PM
Billy Bones,

White vinegar is a class act compared to brown, but high quality 'wine vinegar' at about $12-15(Aust) or $6-7(US), you might be able to dispence with the pumice, and return to a mild soap. Fine for cleaning very soft brushes, little to no residues that I still had with brown and white.

Cheers, Warren.

Tom Dugan
02-20-2002, 07:59 AM
My memory's not that good, but I recall that vinegar is frowned on for cleaning the skin. It washes the epoxy deeper into the pores, where it's more likely to be absorbed, and you're more likely to develop a reaction. At least the pumice just sloughs it all off.

Anyone else heard this?

-T

Will
02-20-2002, 09:22 AM
Oh yeah . You've got to keep the epoxy off your hands to begin with .I think the only way is to buy Nitrile gloves in boxes of 100 , so they're always on hand ( no pun intended ). I used to buy whatever was cheap at the store and they would break at a critical moment when I was forced to carry on . I feel fortunate to have committed my worst indescretions years ago with good ole T88 , a 1 to 1 mix that I think is less dangerous than some others . My hands have been covered in that stuff while doing a lamination I wasn't willing to loose . I came to feel a slight allergic reaction and have cleaned up my act .

Wild Wassa
02-20-2002, 05:58 PM
Just as I was feeling pleased with my new find, two wise heads come along. Thank you Tom and Will. Could I please change an implied reference for the use on body parts to clothing?
Off to do wiser thinking! ....perhapse.

Warren redface.gif

[ 02-20-2002, 06:15 PM: Message edited by: Wild Wassa ]