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Boat Forum / Building / July 2006Remove or Not Remove Partially Cured Epoxy?
I would like to get some opinions on whether I should remove partially cured epoxy in one large area of my deck. Due to my failure to follow instruction in mixing epoxy and failure to do a test batch before using a new type of hardener, I had not thoroughly mixed the epoxy long enough when I installed the core material onto the deck. The result is that the epoxy cures very very slowly: - After one day, I felt that the epoxy was still wet. - After three days, I still could use my thumb to dent the epoxy. - After ten days (today), it is solid enough that I cannot use my thumb to dent it; but I still can use my finger nail to dent its surface. And I definitely cannot sand it yet. What should I do? Should I wait another week or so to see if it may completely cure? I can afford to wait because I can do something else while I wait; but I am not sure if the epoxy will be strong enough even if it is seemingly cured. Should I remove everything and start this over? Unfortunately, this will be very labor intensive to remove the partially cured epoxy. The epoxy is from MAS and the hardener is MAS slow hardener. The brand name may or may not matter. Jay Chan Assuming the curing temperatures are above 60 degrees and it is still rubbery, you are hosed, it will never become hard and will get sticky and nasty in hot weather... Plan on grinding it away... Consider a wire brush mounted on a healthy drill motor (1/2") and lots of elbow grease... MAS is a fine product, I went through a couple of gallons on the past month when I ran low on WEST... denny - who has had every problem possible with epoxy... > Assuming the curing temperatures are above 60 degrees and it is still > rubbery, you are hosed, it will never become hard and will get sticky [quoted text clipped - 4 lines] > month when I ran low on WEST... > denny - who has had every problem possible with epoxy... It's just a gummy mess, but it has to cove off if there are any further layers on top of it. A scraper used like a draw knife will work better. Clean more area quicker. In the end, if this was supposed to be the last layer, (once cleaned!) you will probably want to add another layer - just to get the surface back. Best of luck... Richard > Assuming the curing temperatures are above 60 degrees and it is still > rubbery, you are hosed, it will never become hard and will get sticky [quoted text clipped - 4 lines] > month when I ran low on WEST... > denny - who has had every problem possible with epoxy... The temperature is well over 60. The area is under the sun and is covered with a boat cover, and the area is really really hot inside the boat cover. Therefore, temperature should not have anything to do with this problem. In other words, the epoxy is really in trouble, or I should say "I am really in trouble". I don't think there is anything wrong with MAS. This is just that their Slow Hardener seems to be more sensitive to mixing error (their Medium Hardener is more forgiving). I have been able to get away with mixing not long enough using their Medium Hardener and still get epoxy cured just fine. Unfortunately, when I switched to their Slow Hardener, I forgot to do a test batch first, and I will have to suffer from my own error. Oh well... Jay Chan @#@ It most definitely has to come off. It will never cure properly. Get yourself an small side grinder everyone makes one now, get the rubber backing plate attachment and use very coarse open coat sanding disc 10-60 grit it removes rubbery material fast. Epoxy is notorious for ruining cutting tools and clogging sand paper good luck Ray >I would like to get some opinions on whether I should remove partially > cured epoxy in one large area of my deck. [quoted text clipped - 27 lines] > > Jay Chan Thanks for telling me which tools to use to remove the uncured epoxy. What's a "side grinder"? Is it the same as a surface grinder that another newsgroup member has suggested? I probably will go easy with using power tools; the reason is that the area underneat the uncured epoxy is just a thin layer of the inner skin of the cored deck. I probably want to stick with hand tool such as a green pad, a wire brush, a paint scraper, and white-vinegar. Jay Chan > @#@ > [quoted text clipped - 37 lines] > > > > Jay Chan Unlike the others, I'd vote for trying to get it to cure. A coating on a deck is not structural, but just for sealing and abrasion resistance. I'd try heating up the shop/deck/boat (whatever is easiest) to about 80 F or even higher and keep it that way for a few days. It sounds to me like the cure is progressing, but as others have mentioned, it may or may not cure to the final hardness that you want. I don't think that's a big deal if it gets reasonably hard and you put a couple of fresh coats of epoxy over the top of it ...definitely easier than trying to remove it. Consider this: Even your mostly-cured epoxy is harder and tougher than most plywood plies that people are protecting with epoxy ...why not try to cure what you have and then protect *it* with more layers of epoxy? Brian D >I would like to get some opinions on whether I should remove partially > cured epoxy in one large area of my deck. [quoted text clipped - 27 lines] > > Jay Chan Actually, the uncured epoxy is supposed to secure the core material on the inner skin of the cored deck. Therefore, it is structural. I check it this morning, and I find that the area is still bouncy. I expect that the area should be rigid enough with the combo of the inner skin, the epoxy, and the core material; but it is not. This means I cannot expect it to provide any structural support as a deck is supposed to do. That is not good. On the other hand, you are right -- removing the uncured epoxy is going to be a messy job. I think I will give it one more week to see if will be cured by then -- hopefully. Jay Chan > Unlike the others, I'd vote for trying to get it to cure. A coating on a > deck is not structural, but just for sealing and abrasion resistance. I'd [quoted text clipped - 41 lines] > > > > Jay Chan Jay, I'd say the epoxy has finally reached the 'green stage' . . . about 10 days late, but better then never. True, you really can't *properly* sand it yet - but it proves that the chemical reaction IS progressing. What a lot of people don't realize is that because the epoxy 'curing' is an 'internal conversion' chemical process {as opposed to the 'catalyst additive' of polyester}, a actual 'FULL CURE' can take several months. It's a geometric progression so that after about 72-hours {if everything is done 'per instruction'} it doesn't matter to the typical user. Additionally, because the reaction is rather temperature dependent it can be somewhat controlled. That is sped up or slowed down to almost a 'hibernation' point . . . I've used it as low as the mid 30's, which supposedly you can't do. If time is NOT a problem, and the surface is horizontal {so there is no slippage or 'curtaining'} I'd just wait. Especially as the weather is warming up. When it gets to the point you can't dent it with a finger nail, give it a couple of swipes with some sandpaper. If it still gums up, wait a bit longer and use a 'regular nail' for scratch testing. Use the time to make some small 'test batches' so you get comfortable with mixing {BE THROUGH - this is the MOST prevalent cause of problems}and application. When physically possible, sand and proceed, or sand and 'paint on' a thin cover coat of unthickened fresh epoxy and continue the project. If not this . . . then get yourself a stack of filter masks, a Tyvek suit, a couple of Surform tools & extra blades, belt sander & 'Planer' belts, a 4-1/2in surface grinder, and have at it.!! Regards & Good Luck, Ron Magen Backyard Boatshop {PS - I understand that MAS is quite a bit over-priced for what you get . . . and it's formulated relatively close to where I live} . > I would like to get some opinions on whether I should remove partially > cured epoxy in one large area of my deck. [quoted text clipped - 27 lines] > > Jay Chan When I mix a pot of epoxy, and maybe this goes back to my painting days, I generally mix it really well (scraping sides and bottom with square-tipped mixing stick) then set it on the bench for a couple of minutes to 'kick'. While I do that, I get rollers or brushed together, or wipe down the 'project', etcetera. Then I stir up the epoxy real well (again) and go ahead with using it. I prefer that to just standing there and mixing for 3 minutes and I've never had a failed batch, even with mustard-pump measured 5:1 ratio epoxies (yikes!) Brian > Jay, > I'd say the epoxy has finally reached the 'green stage' . . . about 10 [quoted text clipped - 68 lines] >> >> Jay Chan Glad to hear that there is some hope. OK, I will wait a week or two to give it a chance. Meanwhile, I can always work on something else or go fishing on a rental boat. If after two weeks my finger nail still can make a dent on the epoxy, I will remove it. Also thanks for the suggestion of using a surface grinder. I will look for it in home center. Jay Chan > Jay, > I'd say the epoxy has finally reached the 'green stage' . . . about 10 days [quoted text clipped - 61 lines] > > > > Jay Chan I think there's some confusion between polyester resin and epoxy. As someone else pointed out, with polyester, the hardener is a catalyst/accelerator and the resin will eventually cure. As I understand epoxy, it is the combination of the chemicals in the resin and those in the hardener. Too few of the hardener molecules and you'll never end up with actual epoxy, only with a slurry of cured epoxy and uncured resin molecules looking for their mates. It will not be very strong. I'd suggest you start scraping. Roger (sorry) derbyrm@NOSPAMinsightbbNOSPAM.com http://home.insightbb.com/~derbyrm > Glad to hear that there is some hope. OK, I will wait a week or two to > give it a chance. Meanwhile, I can always work on something else or go > fishing on a rental boat. If after two weeks my finger nail still can > make a dent on the epoxy, I will remove it. Thanks for pointing this out. Sound like I have a hopeless case on my hand. OK, I just have to treat it as a learning experience. Jay Chan > I think there's some confusion between polyester resin and epoxy. > [quoted text clipped - 17 lines] > > fishing on a rental boat. If after two weeks my finger nail still can > > make a dent on the epoxy, I will remove it. > Thanks for pointing this out. Sound like I have a hopeless case on my > hand. OK, I just have to treat it as a learning experience. > > Jay Chan The only times I've had problems like this have been on very humid days. Jay, It's kind of like hypothermic death in the cold climates . . . 'Your not dead until you are WARM and dead . . .'. Absolutely - there IS a chemical structure difference between Poly and Epoxy. However if time is no problem I wouldn't limit the 'wait time' to a week. In addition I would 'add energy to the reaction' by applying heat. There are a couple of simple ways to do this, depending on the area in question. a}Throw a tarp over the area, then an electric blanket set on 'LOW' or 'Medium'. b} set up a 'long board' or 'panel' with several simple sockets for light bulbs. Place it SAFELY & CAREFULLY in the compartment below the deck area. Use 100w or less bulbs. {I use arrangements like this when building in the colder months - with the hull upside down and a tarp thrown over & hanging down to trap the heat, and with a 'drop cord' in a Styrofoam 'cooler' to keep the epoxy components warm}. Once there is NO MORE apparent hardening {after a total of about 30-days or by 'scratch test'}, then I'd make my decision. If it IS 'sandable' {even if you have to do it gently with course paper to prevent 'gumming'} I'd apply a thin coat of CORRECTLY mixed epoxy, then lay in a layer of Dynel. This is NOT like f'glass. It WON'T become clear, but will still look somewhat white. Also without several more coats of epoxy it won't be perfectly smooth. However these are NOT BAD points for a white deck - it won't show and will add traction. PLUS the stuff is VERY abrasion resistant. On the remark about the 'surface grinder' . . . Yes, this is a very useful tool - I have three of them. In your case I would not choose this first - look at the smaller, 'straight-line' BELT SANDERS with adjustable speed. MUCH more controllable, much more sanding material in contact with the surface, less tiring in use, and an all-around more multi-functional tool. Regards & Good Luck, Ron Magen Backyard Boatshop > Thanks for pointing this out. Sound like I have a hopeless case on my > hand. OK, I just have to treat it as a learning experience. [quoted text clipped - 22 lines] > > > fishing on a rental boat. If after two weeks my finger nail still can > > > make a dent on the epoxy, I will remove it. I am sure I will give the partly cured epoxy a bit more time to cure. I am not particularly enthusiastic about removing it. But I will only give it until the end of this month. You see. The temperature inside the tent (where the boat is) is high. I don't believe cold temperature has anything to do with this problem. Therefore, the chance is high that the epoxy may never cure completely. I can afford to wait because I have something else to do anyway. But at the end, I have a feeling that I will have to remove it. I don't quite understand why I should use Dynel instead of regular fiberglass cloth. Is there any particular reason why Dynel is better suit for this situation? Thanks in advance for any follow-up info. Glad to learn that I can use a belt sander instead of a surface grinder. I already has a belt sander with coarse sanding belt. This means I am all set if I need to use a power tool to remove the partly cured epoxy. Jay Chan > Jay, > It's kind of like hypothermic death in the cold climates . . . 'Your not [quoted text clipped - 60 lines] > > > > fishing on a rental boat. If after two weeks my finger nail still can > > > > make a dent on the epoxy, I will remove it. Jay, I just thought of something ...is there any chance that the core material that you are using is incompatible with epoxy? Was it designed to be a core for polyester fiberglass structures? Is it polystyrene? If so, be aware that sometimes epoxy won't cure when in contact with certain other materials. Any chance you can do a test with properly mixed epoxy to see if the stuff will cure? System Three has an epoxy that's designed for surfboards that will cure on a variety of substrates that others won't. If you run into problems, then something like that may be your answer ...with more testing that is. And when you say the tent is 'hot', I'd ask "for how many hours a day". For example, I've got a small repair going on a boat outside the shop right now (Oregon), but the weather has been cool and damp. Sure, it gets up to 70 during the day, but only for a couple of hours and then it cools off all night and morning long. After several days, the medium-speed epoxy is still 'green'. I know it'll cure and if I get room in the shop today then I'll pull the boat in, but epoxy is like growing corn. For a cure, you need to count how many hours ABOVE a critical temperature you get. Your slow hardener will be even worse unless the temperature is even higher... like 80+. Keep us updated ...this is interesting stuff. Brian >I am sure I will give the partly cured epoxy a bit more time to cure. > I am not particularly enthusiastic about removing it. But I will only [quoted text clipped - 94 lines] >> > > > can >> > > > make a dent on the epoxy, I will remove it. The core material (CoreCell) is compatible with the epoxy. I have another area on the deck that I have glued the same core material using the same epoxy, and that has cured very well. One of the reason why that area has cured OK has to do with the fact that I used medium hardener instead of slow hardener and the slow hardener of that brand of epoxy seems to be more sensitive to improper mixing than their medium hardener. The more important reason is that I mixed the epoxy with the full 2 minutes as what the epoxy manufacturer has recommended. Thanks for pointing this out though. Other people who have this problem may be benefited from your suggestion. I live in northern New Jersey, and we have a couple weeks of warm/hot weather (with one cool week in between). In a typical warm day, the temperature inside the boatcover is probably more than 90 degree and may be 100 degree -- yes, I was there once in one afternoon, and I almost got a heat stroke. That's why I am working on building a wood frame to mount an surplus air conditioner right next to the boat. Yes, this is that hot. I will let people know how I end up. I like to post follow-up anyway. I have a feeling that there will be some struggle in removing the uncured epoxy before the story ends. Oh well... Jay Chan > Jay, > [quoted text clipped - 121 lines] > >> > > > can > >> > > > make a dent on the epoxy, I will remove it. Now, this is 17 days since I put the epoxy on the deck. I can feel that the epoxy is more solid than just a couple days ago (my nail still can leave a mark though). I am more hopeful than before that the epoxy will eventually cure. I just need to give the epoxy a bit more time and the coming hot summer will also help. I will let people know how this goes. Jay Chan > Jay, > [quoted text clipped - 121 lines] > >> > > > can > >> > > > make a dent on the epoxy, I will remove it. If I was you, I'd wait a couple of weeks til it seems to harden as much as possible. Then, I'd start scraping. Sicne it hasn't cured properly, you can try a heat gun to soften up the epoxy before scraping. Paint scrapers, window scrapers, utility knives, 40 grit sandpaper. Try everything, except a garden rake.... Seriously. Especially since this is structural, I'd be removing all of the epoxy, down to bare wood, and starting over. cured epoxy is fantastic, but partially cured is a disaster waiting to happen. Why ruin a good boat over some bad epoxy?? Mike Saskatoon, SK > Thanks for pointing this out. Sound like I have a hopeless case on my > hand. OK, I just have to treat it as a learning experience. [quoted text clipped - 22 lines] >>>fishing on a rental boat. If after two weeks my finger nail still can >>>make a dent on the epoxy, I will remove it. Yesterday, I checked the epoxy, and I found that it was noticably more solid than two or three days ago. I have a feeling that it will eventually cure completely -- just very slowly. I have contacted the tech support of the epoxy manufacturer. He said that the epoxy mostly likely will eventually cure because of the fact that the curing is progressing. More importantly, he also said that the cured epoxy will have a good bond despite the fact that the epoxy will take much longer time to cure than normal. Therefore, I will wait a couple weeks for epoxy to cure completely. Jay Chan > If I was you, I'd wait a couple of weeks til it seems to harden as much > as possible. Then, I'd start scraping. Sicne it hasn't cured properly, [quoted text clipped - 36 lines] > >>>fishing on a rental boat. If after two weeks my finger nail still can > >>>make a dent on the epoxy, I will remove it. Now, this is 22 days after I put the epoxy in place. The epoxy is definitely more solid than on late June. I feel safe to have my hope high. The epoxy is curing very slowly. Luckily, I am working on mounting an air conditioner next to my boat; therefore, time is not wasted. Jay Chan > Yesterday, I checked the epoxy, and I found that it was noticably more > solid than two or three days ago. I have a feeling that it will [quoted text clipped - 49 lines] > > >>>fishing on a rental boat. If after two weeks my finger nail still can > > >>>make a dent on the epoxy, I will remove it. Actually, I counted the number of days wrong. I should have said that now is 32 days (instead of 22 days) after I put the epoxy in place. Jay Chan jaykc...@hotmail.com wrote: > Now, this is 22 days after I put the epoxy in place. The epoxy is > definitely more solid than on late June. I feel safe to have my hope [quoted text clipped - 57 lines] > > > >>>fishing on a rental boat. If after two weeks my finger nail still can > > > >>>make a dent on the epoxy, I will remove it. After 45 days since I put the epoxy in place, the epoxy has _finally_ cured completely. Seem like those two very hot days in the beginning of this week really helped the curing process. The outdoor temperature of those two days was 97 degree+, and the temperatur inside the boat cover probably was above 110 degree. Just try to let people know in case someone runs into the same situation as I was. Then he can decide whether he really wants to wait that long for the epoxy to cure, whether he should expect his local weather will help or hurt the curing process, and whether he should work on something else while he is waiting for the epoxy to cure. Jay Chan > Actually, I counted the number of days wrong. I should have said that > now is 32 days (instead of 22 days) after I put the epoxy in place. [quoted text clipped - 63 lines] > > > > >>>fishing on a rental boat. If after two weeks my finger nail still can > > > > >>>make a dent on the epoxy, I will remove it. Jaykchan- Unless you have done some tensile tests on your epoxy, and have found that its strength equals the manufacturer's published figures, your statement that it has cured "completely" is unfounded. Further, it is the height of irresponsibility to suggest that others listening here might rely on the approach you've taken. In my view, you've rolled the dice and whether your boat holds together remains to be seen. Please don't suggest that others take the same risk. Lives could be at stake. > After 45 days since I put the epoxy in place, the epoxy has _finally_ > cured completely. Seem like those two very hot days in the beginning [quoted text clipped - 77 lines] > > > > > >>>fishing on a rental boat. If after two weeks my finger nail still can > > > > > >>>make a dent on the epoxy, I will remove it. The customer service person of the epoxy manufacturer told me that the slow curing epoxy will eventually cure, and the cured epoxy will bond fine when it eventually cures completely. He said this based on the info that he got from their tech people. I have no reason to doubt them because this is their product and they know their products better than I will ever be. If they had said that the slowly cured epoxy would not have bonded well when it eventually curred, I would have removed the epoxy a long time ago. No, I am not worrying. But I will qualify what I said by suggesting that any one who has the same problem to contact the respective epoxy manufacturer to find out their recommendation if their epoxy slowly cured. Jay Chan > Jaykchan- > Unless you have done some tensile tests on your epoxy, and have found that [quoted text clipped - 105 lines] > still can > > > > > > >>>make a dent on the epoxy, I will remove it. You're a patient man, Jay! I've been following along as things have progressed and am very glad to hear that your epoxy finally made the mark. Note that even properly mixed epoxy takes something like 2 months or longer to reach full strength, approaching the mark in an asymptotic way ...90% of the strength within a few days, 100% of the strength in a couple of months. But either way, glad to hear of your good results! Brian > After 45 days since I put the epoxy in place, the epoxy has _finally_ > cured completely. Seem like those two very hot days in the beginning [quoted text clipped - 92 lines] >> > > > >>>still can >> > > > >>>make a dent on the epoxy, I will remove it. Thanks for reminding me that the epoxy will not reach full strength for months to come. I will go easy on the area. From the slow pace that I have been working on the boat, I doubt there will be a lot of people standing on the deck any time soon. Oh well... Jay Chan > You're a patient man, Jay! I've been following along as things have > progressed and am very glad to hear that your epoxy finally made the mark. [quoted text clipped - 101 lines] > >> > > > >>>still can > >> > > > >>>make a dent on the epoxy, I will remove it. > Glad to hear that there is some hope. OK, I will wait a week or two to > give it a chance. Meanwhile, I can always work on something else or go [quoted text clipped - 5 lines] > > Jay Chan If you get a 4" (or so) angle grinder that runs at about 10,000 rpm and a wire wheel that is designed to go with it - it will make glass and epoxy disappear real fast and doesn't clog like sand paper or grinding disks. You can get a cup style brush or a wheel style brush - both work. I have a 4" Makita that runs at 11,000 rpm - Works great. Eye protection and all that... Make sure the wheel is rated for the grinder speed. Even the "correct" brush will throw wires regularly - stay protected. And, these things will remove flesh as fast as they remove glass... -- Geoff The Sea Hawk at Wow Way d0t Com remove spaces and make the obvious substitutions to reply by mail When immigration is outlawed, only outlaws will immigrate. Thanks for the suggestion of using an angle grinder with wire wheel to remove uncured epoxy. I already have an angle grinder. I will look for a wire wheel attachment. I may use it to remove most of the stuff, and then use a ramdom oribital sander when I get close to the thin inner skin of the deck. Jay Chan > > Glad to hear that there is some hope. OK, I will wait a week or two to > > give it a chance. Meanwhile, I can always work on something else or go [quoted text clipped - 21 lines] > remove spaces and make the obvious substitutions to reply by mail > When immigration is outlawed, only outlaws will immigrate. |
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