Air bubbles in my epoxy

[Tar Devil]

I did the search thingy with no luck.

I know this is basic stuff, but I'm ignorant. Why am I getting all these bubbles as the epoxy cures, and how do I stop it?

[Jim Ledger]

It might be outgassing. Applying epoxy when the temps rising sometimes produces air bubbles in the finish, as air in pores and voids below the surface expands and tries to escape.

[switters]

I have experienced the same thing and done my homework thanks to several forumites, and here are the two problems/cures I have found that work well.

One, if you are getting the bubbles in plywood its is going to happen on the first coat no matter what. Get the first coat down and let it soak in and plan on sanding.

Two, let the first coat stay on for a week before applying the next coat, and apply with a squeegee. This makes for an almost perfect (I may have low standards so be careful) coat. Third coat will come out great if you wait again. The epoxy is still cooking off after a few days so you don't want to rush covering a "green" coat.

just advice from a newbie, but it has worked well on the second boat , the first doesn't have a lot of bubbles, thats just my way of making non-skid

Good luck,

[Tar Devil]

Thanks.

First coat did fine (as far as I can tell... I was putting down glass cloth). Second coat went on as soon as I could touch the first, so that may be where the bubbles came from.

I really, really don't wanna wait a week before putting any more on, though...

[AstoriaDave]

First coat did fine (as far as I can tell... I was putting down glass cloth). Second coat went on as soon as I could touch the first, so that may be where the bubbles came from. I really, really don't wanna wait a week before putting any more on, though...

You do not need to wait a week between coats; that is contrary to good practice. It is better to lay on successive coats while within the primary bonding window, while the surface is still capable of chemical bonding with applied resin; the sooner the better, within limits (e.g., still tacky but not readily deformable). If you wait too long, them amine blush can form, and you have to remove it, and sand for a mechanical bond, which is a PITA.

As to the bubbles: sounds like they are coming from inadequate wet-out of the glass. What technique are you using? Are you squeegeeing the glass down and discarding the residue off the squeegee?

Also could come from resin that is beginning to set up.

What resin, what temperatures; what batch sizes, what time in the pot before it is all on the glass?

It is best to get the resin out of the pot ASAP and spread it around roughly with the squeegee and then roll it around allowing it to soak in a bit. Then come back with more resin on the roller over the "dry" spots, moving resin from the over-filled spots. Save back a little resin in the pot and "stipple" over the dry areas with a resin-loaded brush, if needed.

HTH.

[Tar Devil]

I used West epoxy, slow hardner. I only mixed 2 - 3 shots at a time and it hadn't started kicking at all before I exhausted a mix. Temperature was pretty warm but not uncomfortably hot. I didn't squeegee... I put the epoxy down with a brush working into the weave. I was sure I got it adequately wetted, but perhaps not. After wetting out all the glass I went back with the brush and added more where it looked thin.

[cs]

Phil I think that Jim hit on it. Outgassing. Seems like you need to do your epoxy in the evening when the temp is falling instead of rising.

Chad

[John Turpin]

Could be the wood species too. This happens to me on some species of oak. Especially Red Oak.

[Tar Devil]

Phil I think that Jim hit on it. Outgassing. Seems like you need to do your epoxy in the evening when the temp is falling instead of rising.

Chad

It was 9:30 PM.

[Ray Frechette Jr]

Can you imagine a commercial builder waiting a week between epoxy coats?

How on earth could you put food on the table that way? Even if you worked on other boats in the interim, you would have massive overhead to have enough workspace to accomodate all the boats!

Better plan is to find out why you have bubbles forming and eliminate the problem. Maybe you have a fan forced heater blowing across the finish area? I had that problem early on. Solution to that was to deflectt he air from the boat. Or rising tmeperatures from some other source bearing down on the frechly coated boat? I had a time where sunlight bearing down on my frechly coated boat reaised bubbles.

Maybe you are whipping air into the epoxy when mixing it?

Irregardless, bubbles aren;t the end of the world. a quick sanding takes them out, and dollars to donuts you have to sand before painting irregardless. I have never layed down an epoxy coat that cured and I looked at afterward and said "Durn, I think I am going to paint that without sanding it first."


And I know I have never ever contemplated leaving the boat to sit for an entire week before putting epoxy on it again. Customers would go elsewear if I told them the lead time on their boat wouold run months longer because I had to let each coat of epoxy sit undisturbed for a wek at a time.

"The Man wants his boat" is a constant refrain in any commerical boatbuilding operation. In other words, "get off your duff and start doing something to it."

[Todd Bradshaw]

I suspect that you're over-agitating it - either while wetting out the cloth or when using the squeegee to get it down tight and evenly saturated. You may certainly be getting some outgassing, but with slow hardener, those bubbles would mostly float up where you could knock them down with the squeegee before the stuff sets. I'd try a bit slower, smoother technique with the application tools, keeping in mind that introducing air to the mix at any point in the process is likely to cause a bubble problem. As mentioned, you do not want to wait between coats any longer than for the previous layer to stiffen up enough that you don't disturb it. There will be no bubbles forming in the resin from outgassing once it starts to harden.

[switters]

Good thing I don't build boats for a living, just on weekends, which is why dealing with the amine blush and a few scrapes of 100 grit work fine. But while we are on the subject I wondered about the wetting out also. I have read int he past that it is best to let one coat soak in and then wet it out rather than trying to wet out cloth with the first application of epoxy to the bare wood.

part two, I would try the second coat method(mfg recommended also) but I cannot seem to get the timing right. Are there any tricks or tips of the trade that work well for timing the next coat to chemically bond?

Thanks,

[JimD]

Do what Robb White used to do. Pre-heat the boat, either by heating up the work shop to sauna temps, or like I do, which is leave it out in the sun all morning. I'm about to go back outside and epoxy my very warm boat in a few minutes...

[JimD]

Good thing I don't build boats for a living, just on weekends, which is why dealing with the amine blush and a few scrapes of 100 grit work fine. But while we are on the subject I wondered about the wetting out also. I have read int he past that it is best to let one coat soak in and then wet it out rather than trying to wet out cloth with the first application of epoxy to the bare wood.

part two, I would try the second coat method(mfg recommended also) but I cannot seem to get the timing right. Are there any tricks or tips of the trade that work well for timing the next coat to chemically bond?

Thanks,

I choose a sunny day and start mid morning so the the sun has had a chance to warm things up, especially the boat. First, apply a thin coat with a plastic spreader. Go find something to do for a few hours. Then, when the first coat is touch dry, and it should be if its been under a summer sun for a few hours, lay the cloth and wet out, again a thin coat with a soft plastic spreader. Go find something to do for a few hours. Apply a first fill coat. Go find something to do for a few hours. Evening rolls around and apply a second fill coat. Keep boat warm and sheltered overnight. Let boat cure for a couple days, wash, light sand. Done.

[Todd Bradshaw]

Switters, You've got several different issues all rolled up into one untidy blob in that one. Maybe we can pull it apart and clarify them a bit. First of all the "chemical bond". New epoxy will actually chemically bond to previously applied epoxy as long as you don't wait too long to apply it. For most resins, this bonding window will last for several days or more. Resin may seem hard in a few hours, but the cure process isn't usually really finished for a week or more. If you can get the new resin on within two or three days, you have a very good chance of capturing the elusive chemical bond with just about any epoxy. If not, it's not really anywhere near as big of a deal as many people would lead you to believe. Plenty of boats and boat parts (serious, structural components and serious joints, seams, etc.) have been built using pre-coated or pre-fabricated pieces where production time simply did not allow assembly within the chemical bonding window. To prepare these pieces or epoxy-coated areas for fresh epoxy, you simply clean them of any dust, amine blush, atmospheric fallout, etc. then sand them to expose "fresh" clean epoxy, clean them again of sanding dust and proceed to coat, tab, fillet, fiberglass or whatever else you have to do to connect them to the hull. You may not be getting a chemical bond, but you will still get an incredibly strong one that's not likely to ever fail. Don't get too hung up on the whole chemical bond thing. Work at the pace that produces your best quality work. If you are fast enough for a chemical bond, that's great. If not, don't sweat it. There are other ways to skin that cat (did people ever really skin cats? - and why?).

In my opinion, the biggest danger you face when bonding epoxy to epoxy is contamination and some of the most common sources are solvents. Well-meaning builders often attempt to use various chemical solvents to get epoxy "extra clean" prior to subsequent bonding and in many cases it is a mistake. First of all, if you prepare the surface carefully, water works great. It doesn't stink, burn, explode, harm your skin or cost much and it doesn't accidentally leave anything on the surface to prevent a good bond. Leave the acetone and other chemicals on the shelf. You don't need them and they might actually hinder the cleaning/bonding process. Learn to be very picky about what's allowed to come into contact with any epoxy surface that you may want to bond to.

Amine blush - The waxy film by-product that forms on the surface of some types of epoxy as they cure. It's really nothing to fear, but it is something to be aware of and take care of when needed. The easiest way to deal with it is to hot-coat whenever possible. This just means applying resin layer #2 just as soon as layer #1 has hardened enough that you won't disturb it. Any blush that formed on layer #1 will float up through #2. With fast resin, you can add layer upon layer this way in a single day and sometimes get five or six layers on all in one long day - most of which is spent watching resin harden. If you have to stop after a few layers and leave it overnight or longer, the blush will form on the top surface. When you come back the following day, you will need to remove the blush before coating can proceed. This requires a bucket of water, a scotchbrite pad and some sort of clean rags, paper towels, etc. No solvents and no sandpaper are needed. Amine blush is water-soluable, so the water is the solvent. The scotchbrite pad helps scrape it off the surface and you want to use plenty of paper towels to lift the residue off the surface as you go (not just smear it around). You can tell by feel and to some extent by looking if the blush is gone and you'll find that it really doesn't put up much of a fight. If you do happen to "feel" your hull, do it with gloves on. Remember - no stray chemicals are allowed and oil from your skin is one of them.

I use blushing epoxy most of the time (WEST) and one place that I will not stop overnight is after the glass layer goes on, in situations where filler coats will then be applied. A properly saturated and squeegeed fiberglass layer has a lot of weave texture visible. If you then stop for the day, it leaves a lot of small spaces where blush could form and be more difficult to remove. I make sure to get at least one filler coat on the hull before stopping. That first filler will smooth out the texture of the surface a lot and this would make cleaning any blush off much easier the following day.

Even if you use non-blushing epoxy, it's a good idea to clean the surface any time it's been sitting overnight of longer. The water/ scotchbrite/ paper towel method is adequate and likely better than most. Dust, insect stuff, residue from car exhaust and other airbourne yuck do not need to be included in your boat and can detract from good bonding. Chances are, that while you were away something settled on your hull that you don't want there. Clean it off before applying more resin or live with it encapsulated. In general, whether or not a particular resin blushes or not is well down on the list of why I would or would not use it for a particular job and most of the folks who exhibit severe "blush phobia" don't have enough experience with epoxy to take them seriously. They're just repeating something they heard elsewhere as if it's the gospel. The internet and forums like this one are great for stuff like that, posted under a made up nickname.

Finally - pre-coating before glassing: Some do, some don't. Some of us do it sometimes and not other times. Some let it harden and sand it before glassing another day, othere pre-coat and then glass as soon as it's stiff enough. Advantages: It does help control outgassing to some extent and it keeps the wood from sucking resin out of the cloth (the famous, and actually not too common "resin-starved" areas). Disadvantages: Fiberglass fabric often drapes better and adjusts to compound shapes better over bare sanded wood because pre-coating can raise the grain a bit. Pre-coating can also add a bit of weight to the hull and another step to the process. You can try it both with and without pre-coating and decide for yourself which way you like to work. Both will produce good results and I have yet to see evidence that either method is superior.

What's probably more important when appling cloth is staying with it until it's really started to get stiff. Don't slap the glass on and walk away. This is your chance to make sure that the application is OK and that there are no problem spots. Keep looking over the hull as it starts to cure and make sure that you aren't developing problem areas that may be rock hard and not correctable in an hour or two. There is a limited amount that you can mess with hardening fiberglass without just making a problem worse, but with experience you will learn these things. You may be able to poke a bubble with the corner of a squeegee and get rid of it, or stick down a little spot that wants to lift and get it to stay down, but you do want to avoid drastic measure like trying to peel up areas and re-stick them with half-jelled resin or other obviously dangerous moves.

I do apply filler coats as fast as possible, shut the door, turn out the lights (bugs knocking dust off of shop lights) and walk away. I'll never understand why so many people worry about chasing drips in their filler coats. They eventually sand off in a flash once the epoxy work is all done, who cares if there are drips? I'll keep track of my time and check every fifteen to thirty minutes to see if it's stiff enough for the next coat, but the rest of the time, Elvis has left the building.

[Carlsboats]

West lovers may jump on me for this, but as a former West customer I switched to Systems 3 several years ago, and can report that I have no bubble problems, or amine blush either.
I am sure lots of West users have gotten around these problems in their work -- West must have good reasons for having so many loyal customers -- but I switched to Systems 3 for a variety of reasons (ability to intermix slow, medium, and fast hardeners, wide tolerance on temperature limits, simple 2:1 mix ratio, etc.) and in the bargain found that my work set up without bubbles. I asked their tech. people about washing up to remove amine blush, and they said that with the particular resin I was using, there was no such cleanup needed.

[switters]

Thank you Mr. Bradshaw,

[jackster]

Tar Devil,
Good advice above and only a little contradictory, so I'll add mine.(you must decide which; good or contradictory!)
Every 15 mins spent at the 'glass/ epoxy stage in getting every thing even, smooth and fair, will save an hour in the fairing stage, a good investment in my experience.
One tool not mentioned is a grooved metal or plastic bodi roller, used to eliminate bubbles when wetting out the 'glass.
Also, DON'T abrade the 'glass when sanding or cleaning between coats. The idea is to fill the weave so subsequent sanding does not reach the 'glass reinforcing.
I take extra time to get an even cost of epoxy by first rolling fore and aft, then athwart ships, than 45 one way and 45 the other way and again fore and aft, a technique that levels out the coat because of the higher viscosity of the product, followed be a light smoothing with a squeegee.
Hope this helps more then hurts.
Best of luck.

[AstoriaDave]

I didn't squeegee... I put the epoxy down with a brush working into the weave. I was sure I got it adequately wetted, but perhaps not. After wetting out all the glass I went back with the brush and added more where it looked thin.

Here are the problems:

1. You must squeegee to remove the excess resin and move any aerated resin to the edge of the glass and into a waste container. Excess resin adds weight and no strength. Vacuum bagged layups take care of this using pressure from the atmosphere. the best we can do is to make sure the glass is down tight to the wood, and remove excess resin.

2. Use a roller to apply and distribute resin. A brush is way too slow and uneven, and is completely ineffective in "working" the resin into the weave. You only need the minimum amount of resin to wet the glass and bond to the wood. "Painting" on excess resin is a waste of money, adds weight, does not remove bubbles, and does not help wet out. Squeegeeing is critically important. Get a squeegee and use it.

I am still unclear on one thing: is there a cured (at least to the green stage) layer of resin on the wood brfore glassing? If so, then all the comments about outgassing is irrelevant. Once the saturation coat is down on the wood, any bubbles should be gone or trapped. Just glass over them.

[Todd Bradshaw]

Actually there are some well-known strip builders who apply the resin with a brush, rather than a roller - among them is Ted Moores of Canoecraft and Bear Mountain Boatworks fame. However, the brush is not used to "work the resin into the glass cloth". It's used more as a transfer tool in advance of the squeegee - which is what puts the cloth down tight on the surface and removes the excess resin. You can not force epoxy into fiberglass cloth and that may well be part of the problem here. It takes time for the resin to soak the glass and if you try to rush the absorption with any tool, you're probably going to get a lot of bubbles embedded in the glass cloth.

I do prefer a roller (gougeon yellow foam) but it's main function is spreading resin quickly, not working it into the fabric. For squeegees, I cut slabs of ethafoam about 3/8" thick on the band saw. It's a hold-over from my early days when good squeegees were hard to find and I was broke. I do like the feel of them though. They have a nice flexible firmness. Again, whether brushing, rolling or doing the squeegee step, keep in mind that you are trying to avoid agitating or forcing anything. Any action that's too vigorous may be adding air bubbles to the mix.

[Tar Devil]

Well, spit. I din't do it right but too late now. Next time...

[Richard Smith]

Read the article "How-to Make a Transparent Glass Lay-up" on this site:
http://www.laughingloon.com/epoxy.html Best I've seen. The techniques make sense and work.