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Epoxy Tricks


Howard

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As is the case with working with wood, the other component that seems to create a lot of interest from the stitch and glue builders is the epoxy component. With some concern, I figured it might be good to also include an epoxy tips thread similar to the one we have going with tools and jigs. Concern being that this is one area that seems to illicit strong feelings that in some circles can rival such heated discussions of religion and politics. To paraphrase Captain Ron, "this place is full of voodoo, hoodoo and all kinds of w-s (doo)". Hopefully we can keep it civil.

 

As Tom mentioned on the tools thread, Gougeons have provided an excellent resource for folks to follow:

 

http://www.westsystem.com/ss/assets/HowTo-Publications/GougeonBook%20061205.pdf

 

System 3 also offers a similar resource:

 

http://www.systemthree.com/reslibrary/m_published-literature.asp

 

Read both and what you are likely to find are contradictions, and this from the guys who make the stuff. If nothing else, this probably is a good way to point out that in many aspects of working with epoxy, there is no agreed upon right or wrong way of doing things. Only different, and if it works for you, that is all that matters.

 

I have used epoxies from at least 6 different sources and have concluded that some things matter more than others. Others are more of a matter of preference.

 

Rather than start a long post about a lot of things, which I am prone to doing, this topic might be best handled by a number of smaller, individual topic related posts.

 

Remember, keep it civil!!!!

 

 

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Probably not quite what you had in mind, but a question for the group:  I'm using the epoxy Graham provided, which I really like compared to the Brand X I used some years ago.  However, I had some coagulation in the pump of the Part A base epoxy.  It cleaned out with alcohol (and resulting mess), but I'm wondering what caused it.  Too cold (probably sub-60 in the basement recently)?  Or air coming back in through the pump?  Maybe I need to take the pump out and cap the jug if I'm not using it regularly.  This was a white, soft, semi-solid.  Any thoughts appreciated.

 

15-below today here in Milwaukee, with windchills in the 30s/40s below.  "Non-essential" employees like me were told to stay home. So I dream of warm days and gentle breezes on nice boats.

 

p.s. -- thanks for the links.

 

p.p.s.  -- I didn't mean to slam 5:1 Brand X, but I find the 2:1 expoxy from B&B very easy to use and probably better suited to amateurs who dabble.

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Paul:

 

Topics like this is what I had in mind. On the solids and gunked up pumps, that is common. It happens over time, and as you suggest, lower temps are a contributing factor, as is time spent in storage.  And it happens to the Part A resin, not the hardeners. Good news is the stuff is still good.  Solution is pretty easy. Apply heat and it will go clear again. Question is how to apply the heat and how much.

 

For the gallon jug, you might let it sit in hot water for several minutes, up to half an hour or so. The solids will go back into suspension and if you can clear the pumps, all will be well. Option B is to store it in a special place, say an old fridge with a light bulb in it. Maxi version of the EZ bake oven they used to sell for kids, but not nearly that hot. Maybe 75 to 85 degree range. Option C, and extreme care has to be in force for this one, is to pop it in the microwave for a few seconds. You can overdo that in a hurry and there cannot be metal anywhere (caps, foil remnants, etc.)

 

Again, goal is to get it warm enough and the solids will go back into liquid. Anytime your epoxy is getting thick, or it seems stiffer than usual or you are getting a thick, foamy mix after stirring, you probably need to warm up your epoxy Part A.

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To elaborate on Paul's comments about brands, they all have their pluses and minus's and thus all have a loyal following. For those new to this game, it might be helpful to have some background on the subject. Basically, epoxy is derived from petroleum products and of the raw epoxies, there are supposedly only a handful of companies that manufacture the raw epoxy. All the various companies that sell epoxy buy these raw products, then reformulate them for their own purposes (of which there may be hundreds, if not thousands of uses for epoxy, building boats being only one of those, and likely a minor one at that).

 

So basically, most of the companies all start out with the same basic raw ingredients, then reformulate them as they see fit. In our field, there are three major (or at least best known) companies selling to the marine industry. They are: West Systems, System 3 and MAS. There are many others, but if you pick up most supplier catalogs or visit supplier websites (Noah, CLC, etc), these are likely the three you will find most often. Better known also means marketing and likely as not, higher prices.

 

There is a second tier of specialty shops, such as RAKA, Progressive Epoxy Polymers, US Composites, etc. that also sell to the marine industry and individuals alike. Then there are a full pant load of smaller suppliers or users that also sell to the same folks, and I'd put B&B in that category. Nothing wrong with their products (which may be the same, or nearly so as the others), they just don't have as large of a market share as those whose primary business is selling products. Biggest advantage of dealing with these folks is you will likely get good products at good prices. (If you have any doubt, get a small sample and test it).

 

Again, I've used products from at least 6 different companies. I have gravitated to the 2:1 epoxies and of those, have come to prefer those that lean towards the "thinner" or at least less viscous nature. I can't see that these lack any strength......if anything they help when laminating wood and plywood as they soak in deeper, and wet out of glass fabrics is easier. Thinner epoxies also help with air bubble removal, leaving a clearer finish if intended to be left bright. They do run more, so that has to be watched for.

 

The other feature I like is "no blush", although I have heard that under the right conditions, all will "blush" to some degree, some being better or worse about it than others.  No blush helps when you want to coat "hot on hot" without waiting for the epoxy to harden so you can scrub and sand between coats. I think it helps to have a full range of hardener cure rates, from fast to ultra slow........not many offer this range. in my mind, ideally you want the epoxy to remain in a workable range for as long as you need it to, then set up immediately when you are ready for it to. Best change to pull off that nearly impossible trick is to match the hardener to the conditions and the job. Experience will help, but you still need the range of options to help pull it off.

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I have also used a wide variety of different epoxy over time and much prefer the 2 to 1 with no blush. Also instead of using pumps, I use large syringes which is much quicker and more accurate than pumps. Not only that they are much cheaper as well.

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This subject can get pretty complex and technical, but for the average back yard builder, all the major players and secondary formulators offer good products. The differences in physical properties are fairly slight, so it's just a matter of application. For example, Raka's resin seems a tad bit thinner than the others, so it wets out fabric well, but doesn't bulk up film thickness as quickly. A back yard builder's environment can be considered not the best, so non-blush formulation should be taken with a grain of salt, as you'll have enough dust floating in the air, bugs, humidity and temperature concerns that a real expectation of no blush is wishful thinking. Simply put, you'll have to sand the bugs, dust and other surface contaminates out of a freshly applied coat anyway, just because of conditions, so the non-blush thing is over rated. PeelPly can help a great deal in this regard, but it too has it's limitations.

 

I think most back yard builders should look at price and mix ratio, more then anything else. The 2:1's abound and mix inconsistencies aren't as painful. If you're off a little in a 5:1 mix, you might have to scrape off a bunch of still sticky goo in a few days. It's pretty hard to screw up a 1:1 or 2:1 mix. Considering the discount formulators are offering good 2:1's at half the cost of the major industry players, it's a nobrainer as to which way to go.

 

I have an "Building Tips & Tricks" document that I ship with all my plans, that I've recently revised. It covers a number of things, but focuses on epoxy mostly. How to fill holes, lay fabric, mix goo, etc. If anyone is interested, drop me an email and I'll send a copy. It's currently design to print, back to back on 11x17 and fold in the middle, which any office supply outfit can do for little money, or if you have an over size printer (13x19 wide format), you can run it off yourself. I suppose I could set it up to run on 8.5x11 as multiple single pages.

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I've never had a problem with 5:1 mixes, I just measure carefully. I've only recently started using a 2:1 mix and I find that it works nicely too.

Now that peel-ply has been mentioned - What are people using for that? I know there's the peel ply that you buy at the epoxy store, but there's lots of other inexpensive fabric out there. Has anybody tried using a knitted fabric as peel-ply stretched over a compound-curved surface?

And thanks for the offer of the "Building Tips & Tricks" sheet Paul - I'll send you an email.

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I use large syringes which is much quicker and more accurate than pumps. Not only that they are much cheaper as well.

I won't debate the quicker, but doubt seriously they are more accurate than pumps, at least the West System pumps.  I have a set of 301 mini pumps that have been working for 15 years of constant use, so the $12.95 plus tax I paid for them doesn't bother me. I did have to heat one up once with a hair dryer after the resin crystallized from being left in the garage during winter.   And I don't have to figure out what to do with them after I use them.  They sit in my portable epoxy box ready to use again.  Wetting out large areas of glass is the only time I consider using another measuring method.  Had the 306-25 pump in the shop at work, now that was convenience.

 

*knocks on his head I have yet to mix a bad batch.

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Dave-

Are you saying that you take the pump out of the epoxy container after each use and store it in some kind of box? I have been leaving my 2:1 epoxy pumps in the epoxy and hardener jugs, sometimes for a few weeks in between uses and haven't had a problem yet but maybe I need to do that to prevent future problems. In four months I have replaced the pumps once because I sensed that one of them was compromised.

Thanks

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I have purchased pumps from four different suppliers and have found them to all be accurate. Best advice for testing them for accuracy came from MAS, which recommended a simple calibration test. After the pumps are fully primed, put one pump of Part A in a small clear cup. Put two pumps of Part B in a similar cup, then either measure (if the cups were graduated, such as medicine cups) or side by side if they are clear. If the volumes are equal, you are getting 2:1. I would just trust the West System pumps to be accurate. It would be a rare fluke if they are not.

 

The biggest problem I had with the West Pumps was when I was pumping large amounts from the small cans. I would make the mistake of running maybe 5 pumps of Part A, then on the 2nd or 3rd pump of Part B, the can ran out (and always with several ml left in even the small can). Any attempt to save it from there was a guess. Solution to that (and all other pumps), is to make one pump from Part A, then one pump from Part B. If you need 10 pumps, it is always one pump Part A, one pump part B until you get there. That way, if you run out somewhere along the way to your 10 pumps, the entire batch is not going to be ruined. With the 2:1 epoxies, there is enough margin of error that a batch can usually be saved.

 

My preference is also a jug that is transparent enough you can see through it. That way you always know how much you have left and can also see if there are solids on the bottom, or if the solids are dissolved. During periods of cold weather (like now), you can also get a feel for how thick or thin things are going. For some reason, MAS is now using solid white jugs (I hope there is a reason for that unrelated to marketing). But the same thing would apply to any supplier using cans.

 

But as for the problem of bad epoxy, if the product came from a reputable source, you can almost always assume any problems you are having are related to operator error. Either an incorrect mix ratio or not mixing enough or using the wrong products for the conditions.

 

The only product related issue I can think of is if you are pouring from the jug (instead of pumping) and have a layer of solids on the bottom of your Part A jug and you pour some of the remaining liquids from the top. I don't know what is in those solids relative to the liquids. You may be messing up the whole jug by doing that. 

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Dave-Are you saying that you take the pump out of the epoxy container after each use and store it in some kind of box?

No Lennie, I keep my resin cans with pumps installed along with cans of fillers, mixing cups, chip brushes, gloves, etc. all together in a wooden storage/carry box I made.  I use epoxy a lot at work and on my personal projects.  This box and the installed pumps make using epoxy down right convenient.

 

The only product related issue I can think of is if you are pouring from the jug (instead of pumping) and have a layer of solids on the bottom of your Part A jug and you pour some of the remaining liquids from the top. I don't know what is in those solids relative to the liquids. You may be messing up the whole jug by doing that. 

I have never seen resin settle out nor heard of such case till you just mentioned it Howard  I am not sure it even can settle out.  If the solids in the bottom are crystallized resin due to cold, then it should not matter that you pour off the top.  But to be safe just heat the resin jug by putting it in a bucket of warm water.  If it is crystallized resin then it will clear up by itself.  You may want to stir it up too, but I have never found it necessary.

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Second issue with pumps, is how much volume they produce per pump. I have two different pump sets I'm pulling from now and one set produces 45 ml per pump (combined Part A and B ) the other 15 ml. If you want only want a 15 ml batch (or smaller) from the first set, you might be out of luck. If you want 250 ml batch from the second set, you would be in for some serious aerobic exercise.

 

Even if pulling from pumps, there are times when it helps to have some graduated cups (both large and small) you can pump or pour into. I use graduated medicine cups on the small end (can go as low as 7.5 ml combined) and larger, clear plastic cups on the large end. You could also use the pint or quart sized graduated mixing cups, but those are more expensive and difficult to clean up than you might think.

 

On the clear drink cups, they are inexpensive and can be calibrated by hand to match any volume you want. It is a two cup system. Place one cup inside the other. The outside, or bottom cup gets calibrated and saved. To calibrate, pour a known volume (say 60 ml) of any liquid.....water works......into the inside cup, then mark that level on the side of the bottom or outside cup. Then pour in half that amount (say 30 ml) and mark that volume, again on the outside cup. Combined, you now have a calibrated 90 ml volume cup that you will save. So in the future, anytime you need to mix 90 ml of epoxy, put a clear cup inside, the start pumping or pouring.

 

I have found that about half the volume of the inside cup is as much as you want to go. Any more than that, look for a larger cup. You need the head space for mixing and especially so if you are adding any thickeners such as wood flour, etc.

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Dave:

 

It is the content of the crystallized stuff on the bottom I'm worried about. I don't know the chemistry well enough to know if that is all epoxy, or only one of the components of it. I do know the tendency to form solids differs by product. I had two different quart sized jugs of MAS epoxy sitting on the same shelf. Both purchased the same time. One was the FLAG version and one the Low Viscosity. The FLAG was bad about solids forming. It went early and often. Was always heating it up to use it. The Low Vis never did. In fact, the remnants of that small jug are still sitting on the shelf and after 5 years, has still never formed solids.

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Another question is "how much to buy" and when? If you need 5 or 10 gallons for a build, do you buy it all at once or space it out?

 

Considerations would be:

 

How long is it going to take me to build? Months? Years?

 

Volume discounts?

 

Other?

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might as well buy as much as you think you'll need all at once, depending on pricing of course. It doesn't spoil. I've used epoxy that was 5 years or more old, no problems. Now the hardeners may darken, West fast in particular-it'll turn a dark purple. So if  trying for a clear finish, don't use that. But for gluing, etc, or coating under paint, no problems.

 

When I was building the 35 foot tri, I was ordering WEST 10 gallons at a shot- was cheapest way at the time.

 

Lately, I've just ordered from B and B. I'm totally happy with the product.

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If epoxy has crystallized, warm it up and the chemical crystallization will recombine without issue. The crystallized molecules are heavier then the surrounding liquid molecules, so they sink. This means you can "pour" off the top. Epoxy formulations that have viscosity modifiers are more prone to this then others.

 

The use of pumps can be hit or miss, but even the formulators recognize there can be an issue with long term reliability. If you really use a lot of goo, the pumps are a pain in the butt. It's one thing to use 6 pump batches frequently, but a bother to push a couple of quarts through the pumps for a batch. If you do use pumps, keep them clean. It's also helpful to insure the prime with partial strokes, until goo appears. This way you can insure full strokes and an accurate mix, with only a few drops of waste as you restore the prime.

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When I was using pumps I would always have TWO resin bottles and TWO hardener bottles going. Before dispensing material into the mixing cup I would pump a few priming strokes from one resin bottle to the other and from one hardener bottle to another. Since I wasn't wasting any resin or hardener in the priming process I was happy to prime a lot to make sure there were no bubbles in the pumps.

I bought epoxy in big containers but used smaller ones to dispense it.

These days I use the self-graduated cups that Howard described. I like that method because I'm no longer limited by the size of the pump. I usually put several scales of graduation spaced around the cup so I can mix up various size batches.

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Have attached some photos of the homemade mixing cups. Best to use the straight sided (meaning no ribs), clear cups. Not always easy to find, so buy plenty when you find the right ones.

 

The opaque cups will work, but once you stack one inside the other, visibility is poor and you will have a tough time seeing the level. In either case, avoid any cup with ribs. They distort things as the volume level in the cup passes over the ribs.

 

I like Ken's idea of calibrating several levels on the same cup. You could easily have 4 or more amounts on the same cup. Do not screw up and get them inverted, putting the calibrated cup on the inside. Aside from the fact your mix will be off, you have just ruined your cup and get to calibrate a new one.

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Howard - 

thanks for the photos.  This will be on the "to do" list this weekend as I glass the interior of my CB case.  

 

The other thing I ran into during my last build was that certain finishes do not play well with an epoxy substrate.  A polyurethane varnish softened up my nicely epoxied gunwales and I had to the whole job again. Switching to a traditional spar varnish with a high UV content solved the issue and looked great when done.  Maintenance has been a simple sand and recoat with varnish each year for the past 5 years.  

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I don't like epoxy under varnish or any other clear coat on solid wood trim at all.  I do like it for plywood decks and other surfaces on dinghies like Grahams. 

 

Wood trim often wears or is dinged during boat use.  Now you have worn through the epoxy as well as the finish coats.  Real varnish, my favorite,  can be easily stripped with a heat gun and refinished to look brand new.  Epoxy can not.  And no matter how you try to refinish the ding or worn area through the epoxy it never blends in really well again.  So even though it seems to be less maintenance over a medium period of time a major refinish will be obscenely difficult, time consuming and tedious.

 

Large flat surfaces like plywood decks and such will rarely be damaged if the boat is used with care.  The epoxy may even help prevent damage to the top veneer.  If the plywood surfaces are damaged at all significantly, then the top veneer is usually damaged to the point that refinishing won't help anyway.  I think this is a great application for epoxy over bright work.

 

  The other thing I ran into during my last build was that certain finishes do not play well with an epoxy substrate.  A polyurethane varnish softened up my nicely epoxied gunwales and I had to the whole job again. Switching to a traditional spar varnish with a high UV content solved the issue and looked great when done.  Maintenance has been a simple sand and recoat with varnish each year for the past 5 years.  

 

Varnished solid wood trim will maintain by simple sanding and recoat just fine without epoxy underneath it.

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