Confused by epoxy

[Victor Robinson]

Specifically, West System.

I'm making a coffee table out of reclaimed wood, and the boss has requested that cracks and gaps and knots in the wood be filled, but since they add character, we're looking to fill with something as clear as possible.

I figured West System epoxy might be a good way to go, but having never worked with the stuff before, I'm a bit confused as to which product(s) would be best for this application. I'm looking at their offerings on the Lee Valley website...any help would be appreciated.

http://www.leevalley.com/US/wood/page.aspx?p=20016&cat=1,110,42965&ap=1

[Thomas S Stockton]

go to the west system web page they have a lot more info http://www.westsystem.com/ss/

[Kent A Bathurst]

I think you want the 205 or 206 hardener. How fast do you want to it to kick?

On a related topic - when I use epoxy, I mix it up and spread it out on a plastic picnic dinner plate, then set the plant on top of a pan full of ice. That brings the cure rate to about zero - plenty of time to get it applied, then the temp rises, and off we go........So I wouldn't worry with either hardener system, if you take that route.

Caution: if you use, say, a baking pan from the kitchen, and SWMBO is home, put the pan in a plastic trash bag, then put in the ice, so the pan is protected. If she is not home, you don't need the trash bag, because you won't have all the drama to deal with while you are working it up. :D

[Mike Ontko]

Kent - it sounds as if there's another story hidden between the lines of your cautionary statement :)

[John Donhowe]

Ooooooh! I like that ice trick- nothing quite as exciting as racing to get epoxy on your project while it's beginning to harden :eek: Any reason that wouldn't work with Bondo, as well?

[Allan Speers]

On a related topic - when I use epoxy, I mix it up and spread it out on a plastic picnic dinner plate, then set the plant on top of a pan full of ice. That brings the cure rate to about zero - plenty of time to get it applied, then the temp rises, and off we go........

Say, that's a great idea, Kent !

[Allan Speers]

Victor,

Using clear epoxy on very small knots & defects works great. However, be careful if you need to fill larger areas & cracks, because most epoxies don't have any give to them, and so the repairs can crack later.

One epoxy product that definitely does flex is "Gluvit." http://www.marinetex.com/gluvit.html

[Victor Robinson]

Alright, fast-cure kit it is! (thanks to Kent's ice trick)

I was probably overthinking this...got confused by all the fillers and additives.

Thanks gang!

[Steve Peterson]

You will probably want to mound up the epoxy and sand it off so it is flat. It will try to self level, so it really only builds up about 1/16" above the surface. It is OK to go back and fill in a few holes where the epoxy kept flowing into the hole. Add a piece of tape to the bottom side if the holes go all the way through. This will avoid you having a coffee table glued to your workbench. Flip it over in an hour to fill in the holes on the bottom.

Epoxy sands fairly easily, but may be harder than the surrounding wood so you will have to be careful to not dish out the wood while sanding. You may want to sand the "overflow" epoxy completely if you are planning to stain. Normal finish doesn't look too bad over epoxy, but stain may react differently to areas where epoxy soaked into the wood if it isn't completely sanded out.

Steve

[Jim Dwight]

I use cheapo 5 minute epoxy from Harbor Freight. It is pretty clear.

[Peter Quinn]

Use the 105 epoxy and the 207 clear hardener for the best knot filling properties. If this is for stain grade projects, the other hardeners produce through their reaction and cure what is called aniline blush. It gives a slightly cloudy appearance to the cured patches, but more importantly it is caused by a water soluble wax that forms as part of the curing of mot epoxies, and that wax will cause problems with clear finishes that go over it. I learned this the hard way. You can remove the surface wax by scrubbing with warm water, if you don't you will get craters and fish eyes where you used the epoxy, best to avoid this. They sell the 207 hardener in some pretty small quantities, so if you plan to do some less visible structural work with epoxy you could certainly use the appropriate speed of hardener for your climate conditions and work process, but for filling and priming the 207 is best.

[Allan Speers]

Epoxy sands fairly easily, but may be harder than the surrounding wood so you will have to be careful to not dish out the wood while sanding.
Steve

Indeed. For this reason I like to use a scraper, or even just scrape with a razor blade.

[Andrew Hughes]

Here's the stuff I use I don't remember how much it cost but I remember it's expensive.The bigger the batch the faster it hardens so Kents ice trick is a good one.

[Kent A Bathurst]

Kent - it sounds as if there's another story hidden between the lines of your cautionary statement :)

I don't think it was hidden at all, Mike. :p

I just do what I can to pass on lessons learned to my fellow adventurers...........avoiding the drama is always worth the effort, IMO.

Or, consider buying "your own damn stuff", as it was once suggested to me. Hence my own:
> iron [premelt edging];
> double boiler [heating oil, beeswax, a mason jar with leftover cold coffee, etc.];
> a roll of waxed paper [for obvious reasons].
> second hand yard-sale coffee grinder [shellac flakes];
> and one of those "one time" aluminum cooking pans at the grocery store for the epoxy ice trick.

I still borrow the nutrition digital gram scale for shellac mix.....but I get the evil eye each time she slooooooowly hands it to me......cover it with a big sheet of waxed paper, even though shellac flakes are a solid, and are edible.........

But - all of these items together don't come close to the last plane I bought - LN 4-1/2C, here on the creek. So - what the heck? Keep the peace, no drama.

[Kent A Bathurst]

Here's the stuff I use I don't remember how much it cost but I remember it's expensive.The bigger the batch the faster it hardens so Kents ice trick is a good one.

It is an exothermic cure - gives off heat, which accelerates the cure.

So - one big lump in a mix cup versus spread thin on the plastic plate - that slows it down right there. Then the ice takes care of the rest.

[Kent A Bathurst]

Ooooooh! I like that ice trick- nothing quite as exciting as racing to get epoxy on your project while it's beginning to harden :eek: Any reason that wouldn't work with Bondo, as well?

I imagine it will do the same, John - also an exothermic reaction, but with polyester and hardener, v epoxy and a different hardener. the spread thin over ice just serves to fight off them pesky exotherms.

[Larry Edgerton]

Use the 105 epoxy and the 207 clear hardener for the best knot filling properties. If this is for stain grade projects, the other hardeners produce through their reaction and cure what is called aniline blush. It gives a slightly cloudy appearance to the cured patches, but more importantly it is caused by a water soluble wax that forms as part of the curing of mot epoxies, and that wax will cause problems with clear finishes that go over it. I learned this the hard way. You can remove the surface wax by scrubbing with warm water, if you don't you will get craters and fish eyes where you used the epoxy, best to avoid this. They sell the 207 hardener in some pretty small quantities, so if you plan to do some less visible structural work with epoxy you could certainly use the appropriate speed of hardener for your climate conditions and work process, but for filling and priming the 207 is best.

Ditto what Peter said.......

Call West and ask for a manual, They are free and you will know everything you need to know about using epoxy when you read through it, and you will understand what specific products to use for each application. If you are still stumped they have the best hotline that I have ever had the pleasure of dealing with.

Larry

[ian maybury]

There's quite a bit of devil potentially in the detail with epoxies Victor, so I wouldn't say you were overthinking it. Most manufacturing engineers with experience would probably argue that the major downside with adhesives is the way that an unforeseen and uncontrolled variable can so easily mess things up.

There's a lot of different hardener systems which tend to deliver different properties in the cured resin, and a lot of factors that can cause problems. This seems a decent summary, but be guided by the relevant maker's tech support. Be careful they know their stuff as it seems like the office junior sometimes gets the job : https://protective.sherwin-williams.com/pdf/Epoxy%20Coatings%20Guide.pdf

Water (not a solvent like acetone or cellulose thinner) as Peter and the guys removes the waxy layer/amine blush, but if possible it's generally better to pour all of the material in one shot - using a tape or similar dam to contain it. Which makes it hard to judge the levels. Alternatively apply the next layer before the first has fully cured and the blush has emerged.

Another factor that introduces some risk regarding how well the stuff bonds to itself is that the components combine to a fixed ratio. Get it slightly wrong or fail to perfectly mix it (which almost by definition must happen) and the surplus tends too ooze up through the surface. Significantly wrong and it'll also weaken the cured material. Which is another reason why water then solvent washing and sanding before re-coating at minimum is wise.

Kent is correct about cooling (or at least ensuring that the mix is spread out in a thin layer before use so that the heat given out by the cure doesn't warm it up) slowing the cure, but the catch 22 is that it's important to ensure that it's fairly warm while curing to get proper polymerisation and hardening. (check the data sheet, and stay well above the recommended minimum temperature) This also thins it enough so that it spreads easily, penetrates well and quickly releases air bubbles trapped during mixing. Poor polymerisation tends to show up as a tendency to gum sandpaper among other things - while epoxy that's heat cured sands and polishes beautifully. It's actually recommended in some cases that the stuff is heated to quite a high temperature to get the best possible cure - maybe up to 50 deg C.

The requirement for some heat to drive the cure arises from the fact that the element of the cure that kicks off polymerisation by (i seem to remember) making available a supply of the right sort of ions is a bit like an alka-seltzer - it'll run out of fizz before the polymerisation/cure is complete at low temperatures. Too warm in a reasonable volume though and the mix will overheat, burn and give off nasty fumes - so testing is advisable.

Warming while helping with the bubbles and the cure greatly reduces the viscosity/thickness of the mixed resin, which is one reason why a dam or enclosure (and no leaks out of the bottom of the hole) are pretty much essential.

I've had good luck with using a slow curing resin, and keeping the mix coolish (low room temp and not cold) and spread out before use - for lots of working time. Then by kicking off the cure (it can drop the cure time to only a fraction of that listed) by making sure that the piece is nice and warm before the resin goes on - and keeping it that way until the cure is complete with e.g. an oil filled radiator in a small room. Possibly even by parking the joint (if it's of a suitable size and material) in a low oven once the resin has gelled so it's not going to run everywhere - but is still in the early stages of the cure. (be guided by the maker's max/min recommended temperatures)

There's numerous fillers commonly used in epoxies to thicken them into pastes for forming fillets etc (fumed silica or micro balloons are common - neither are good to breathe and this may be helpful: https://www.youtube.com/watch?v=cTuXBt7uIeM ), but they pretty much universally will produce a cloudy or even opaque material - so not much use for what you have in mind. You'll almost certainly end up working with an unfilled liquid resin. Epoxy adhesives like Araldite are likewise typically filled with something that makes them cloudy - so not generally suitable either....

[fiona beckett]

I use cheapo 10 minute epoxy from Harbor Freight. It is pretty clear.
http://wigunpics.science/16/g.png

[Bill Adamsen]

Also, do the pour if possible as the temperature is falling ... rising temperature tends to drive moisture out of the wood which becomes entrained air bubbles in the clear mix. I have found filling cracks doesn't require any "fillers," that is, the light seems to get trapped in the recesses of the crack and it appears dark. I do use the different thickeners and fillers for their various properties when glueing up. I also use the graphite dust for flat black coatings. Just follow the Gougeon use guides (http://www.westsystem.com/ss/use-guides/)or book (http://www.westsystem.com/ss/assets/HowTo-Publications/GougeonBook%20061205.pdf) and you won't go wrong.

[Leo Graywacz]

Use the 105 epoxy and the 207 clear hardener for the best knot filling properties. If this is for stain grade projects, the other hardeners produce through their reaction and cure what is called aniline blush. It gives a slightly cloudy appearance to the cured patches, but more importantly it is caused by a water soluble wax that forms as part of the curing of mot epoxies, and that wax will cause problems with clear finishes that go over it. I learned this the hard way. You can remove the surface wax by scrubbing with warm water, if you don't you will get craters and fish eyes where you used the epoxy, best to avoid this. They sell the 207 hardener in some pretty small quantities, so if you plan to do some less visible structural work with epoxy you could certainly use the appropriate speed of hardener for your climate conditions and work process, but for filling and priming the 207 is best.

Yes 105 and 207 are what you are looking for. The 207 is designed to have a finish applied over it.

[Peter Quinn]

I like the theory of Kent's ice trick...but its dead wrong for priming and filling. Ever try to spread cold epoxy? Its like cold peanut butter. Not going to just drop into all those cracks effectively. Bill touched on this. The problem is air bubbles, its the tell of a bad patch. I had to do a bunch of epoxy filling/priming at my last job, read the entire Gougeon manual, watched the videos, combed the internet. WE had had some very poor results, lots of bubbles, craters fish eyes. Anybody that tells you sanding out epoxy is fun...is lying.

When you mix epoxy it traps air bubbles. As epoxy cures it heats. As you heat air it expands. Expanding air in the epoxy gets trapped as it gels...thats bad. Cold epoxy is thicker, thick epoxy traps more air, so you get more bubbles. If you are trying to extend the pot life of batch of epoxy so you can do non visible structural glue ups, non of this means much and the ice probably rocks. But if you are priming or making cosmetic fills...you don't want ice, you want heat. Heat the resin to around 105 degrees, that makes the mix nice and thin, it fills well, and any bubbles are small, rise quickly through the thin mixture and pop easily. Then move your ass, because at 105 degrees it goes awfully quick. Seriously, this is not work for the sluggish. Mix small batches, get it all in quick and don't dawdle. It turns out a nearly crystal clear fill, makes a great primer for things that require the water resistance (did a bubbling shower door once). I used to put the pot of resin on a metal shelf over an electric strip heater and check its temp with a non contact thermometer. I almost bought a baby bottle warmer, not sure those get hot enough? Save the ice for your beer.

[Dave Cav]

I don't think it was hidden at all, Mike. :p

I just do what I can to pass on lessons learned to my fellow adventurers...........avoiding the drama is always worth the effort, IMO.

Or, consider buying "your own damn stuff", as it was once suggested to me. Hence my own:
> iron [premelt edging];
> double boiler [heating oil, beeswax, a mason jar with leftover cold coffee, etc.];
> a roll of waxed paper [for obvious reasons].
> second hand yard-sale coffee grinder [shellac flakes];
> and one of those "one time" aluminum cooking pans at the grocery store for the epoxy ice trick.

I still borrow the nutrition digital gram scale for shellac mix.....but I get the evil eye each time she slooooooowly hands it to me......cover it with a big sheet of waxed paper, even though shellac flakes are a solid, and are edible.........

But - all of these items together don't come close to the last plane I bought - LN 4-1/2C, here on the creek. So - what the heck? Keep the peace, no drama.

Add to the list:
Sewing machine
Box of mason jars (or two, pint and quart)
Boxes of zip lock bags
Thrift store/Goodwill pizza pans, pie pans, cookie sheets

[Mike Hollingsworth]

I prefer system 3 over west system.
much easier mix.

I always fill with black.
Everything else looks phony.

[ian maybury]

:) While we're on a roll. A good supply of disposable syringes and shallow mixing cups is good too. Possibly go for the hand pump/measure equipped cans of resin if using large volumes.

Methanol or isopropyl alcohol are good for thinning mixed epoxy resins up to about to 10% when coating or making very thin laminations, and working in fairly warm conditions. Probably not a good idea if filling holes and the like though - chances are it wouldn't flash off fast enough to avoid becoming trapped with unpredictable effects. Alcohol is also good for cleaning brushes.

Disposable gloves too. Don't handle the stuff while it's liquid, while it depends a little on the exact cure system in use it's famously good at triggering allergic reactions which may result in an ongoing problem with the stuff. (sensitisation)

[Bill Adamsen]

While I have used a fridge to cool epoxy, that was probably 25 years ago. I have - like Peter - just learned to work quickly with small batches. And as he indicates, you want to be very careful not to entrain air bubbles if using for coating (207 hardner). Same practices you would use for varnish or poly ... stir slowly, don't tip the brush in your container. Heating works well, just don't do it in the microwave. I've tried. Not recommended.

Hinting at what Peter says about removing too much epoxy, you can cut (with a knife or other sharp blade) epoxy before it has fully cured. This is a great way to trim dynel or glass cloth. In general with epoxy the motto is (use) "less not more."

[Kent A Bathurst]

I like the theory of Kent's ice trick...but its dead wrong for priming and filling. Ever try to spread cold epoxy? Its like cold peanut butter. Not going to just drop into all those cracks effectively.

True enough. The bit I left out is that as I am ready for it, I pile up a fair sized glop, or put some in a small mix cup, and allow it to start cooking off the ice - it will warm up and lower viscosity.

The ice tray thing is there just to assist when you are not comfortable that you can keep pace with the cook.

I'd agree that it might be better applied to joint assembly - I can apply thin layers via tongue depressor on tenons. And keep the batch on ice as I move through the joinery. But - I have done it for filling also. Just sayin'................

[Larry Edgerton]

But - I have done it for fillings also. Just sayin'................

A guy could save on dental bills that way I guess........

[Victor Robinson]

Wow, lot of great info here, thanks everyone.

Ok, since I will be applying stain and finish (WB conversion varnish), I guess #207 is the way to go if going with West System. Though quite frankly I think I'm going to do an experiment with the Harbor Freight epoxy, stain, and finish and see how that goes. I do intend to invest in some serious epoxy eventually but this project doesn't necessarily warrant it if I don't need to.

[Peter Quinn]

True enough. The bit I left out is that as I am ready for it, I pile up a fair sized glop, or put some in a small mix cup, and allow it to start cooking off the ice - it will warm up and lower viscosity.

The ice tray thing is there just to assist when you are not comfortable that you can keep pace with the cook.

I'd agree that it might be better applied to joint assembly - I can apply thin layers via tongue depressor on tenons. And keep the batch on ice as I move through the joinery. But - I have done it for filling also. Just sayin'................


The ice idea made me smile, before the last shop I was at got AC in the entry/passage door shop, we used to keep the adhesives in the fridge! Titebond III and West systems both got refrigerated, it was the only way you could ever get an assembly together on a 90 degree day. A bucked of ice may have been handy at the bench, or perhaps a cold cozy on the glue bottle? Used to get real close to 100 too many days. I love cold glue for big assemblies.

First time I ever mixed west systems, I made some pretty classic mistakes. Used a plastic paint mixing quart container. Bad. Mixed way more than I needed, maybe 1 1/2 pints for a small glue up, so a tall column of epoxy in plastic container. Bad. And being always in a rush in my younger days, I figured if I hit the mix with a few extra shots of hardener, even better, it would cure quicker! Bad. Only thing I did right was mix it and give it the requisite 5 minutes to kick before application. Didn't want to waste any time, went to the slop sink to clean up something while I waited...came back to the bench to find a smoking hell pot in a melting plastic container that was oozing on the bench, a mix of melted plastic and hot epoxy! I scooped the whole mess into a cardboard box and rand for the exit, hucked it out the door onto the lawn before what I imagined was an inevitable explosion. Got a standing ovation from my fellow shop mates...not the good kind!

[Allan Speers]

Thinking about both Ian and Peter's posts, above (wow...) and the possible occasional need for a thinner epoxy:

I'm wondering if anyone has ever used Xylene, and then applied a finish? Xylene thins all epoxies, AFAIK. Though it also weakens the joint a little, I've used it successfully to repair some deep cracks in my workbench, and a few other items. However, I've never used it to fill voids in furniture before finishing. (I've never needed to thin it in such cases.)

Has anyone, and if so, did it cause any problems such as fisheyes?

[Larry Edgerton]

T
First time I ever mixed west systems, I made some pretty classic mistakes. Used a plastic paint mixing quart container. Bad. Mixed way more than I needed, maybe 1 1/2 pints for a small glue up, so a tall column of epoxy in plastic container. Bad. And being always in a rush in my younger days, I figured if I hit the mix with a few extra shots of hardener, even better, it would cure quicker! Bad. Only thing I did right was mix it and give it the requisite 5 minutes to kick before application. Didn't want to waste any time, went to the slop sink to clean up something while I waited...came back to the bench to find a smoking hell pot in a melting plastic container that was oozing on the bench, a mix of melted plastic and hot epoxy! I scooped the whole mess into a cardboard box and rand for the exit, hucked it out the door onto the lawn before what I imagined was an inevitable explosion. Got a standing ovation from my fellow shop mates...not the good kind!

Had pretty much the same experiance, with the exception of I work alone so no witnesses. No more red Solo cups for me! Thats how we learn.........:rolleyes:

You can put your resin and hardener in a cup to get ready, and as long as you do not stir them up the exothermic reaction will not start. I get my mix in the cup, go through my whole process in my head and have everything ready, then just before application mix the two parts.

[Leo Graywacz]

I cut a soda can in half to use for the vessel. Works great and then you throw it away with no concerns.

[Larry Edgerton]

I cut a soda can in half to use for the vessel. Works great and then you throw it away with no concerns.


Ditto........

Sometimes beer cans.:p

[Kent A Bathurst]

Ditto........

Sometimes beer cans.:p

Beer in CANS!?!?!?!

What - PBR and Old Style? Hamm's Light maybe for a special occasion?

Yeesshh. :D

[ian maybury]

Hi Allan. I'm not a chemist, so this is only a broad and not very expert view.

The viscosity of epoxy resins is typically rapidly reduced by even moderate (5%) thinning, but i'd as before be reluctant to use this methods for more than thin coatings. I've for example used epoxy resin thinned with methanol as a controlled means of applying thin coatings to seal very fine glass cloth skins on high performance competition model aircraft where weight is critical - you can brush on a fairly wet looking coating, but when the alcohol flashes off what's left is nice and thin.

The key is that the combination of the volatility of the solvent and the thin resin coating allow the solvent to flash off before it sets. Even so solvents typically weaken the polymer and have other side effects as outlined in the West document at the first link below, so it's a case of proceeding with caution in suitable circumstances. I'd want to ask tech support about your Xylene.

Most coating and laminating resins that we see tend to have fairly similar viscosities. They are however greatly thinned by increased temperature, and this on warmed work (combined with a slow hardener so the heat doesn't kick it off too fast) is often enough where penetration and wicking are required.

There are some differing epoxy resin and hardener chemistries which make possible resins ranging from very low to very high viscosities - even without filling. Googling 'low viscosity epoxy' brings up lots of links. Low viscosity epoxy resins are for example made by numerous companies for potting and coating in electronic applications, and for jobs like impregnating samples before sectioning and the like. I haven't used these, and don't know what structural and other performance constraints the differing resin types may bring - but a call to tech support at Masterbond or the like in the second link below should generate some feedback. They are probably quite a bit more exensive than the grades sold for boat building and the like, but judging by comment i've seen may not be hugely expensive...

http://www.westsystem.com/ss/thinning-west-system-epoxy/
http://www.masterbond.com/techtips/optimizing-viscosity-epoxy-adhesives-potting-compounds-and-sealants

[lee cox]

I am reading this thread with great interest as I am looking for the old Elmer's epoxy which had the blue and orange tops with white tubes. You had 24 hours for cure time. I used it to fill cracks in gun stocks and furniture. It was clear with a yellow brown tint and blended well. The little wide tabs on top of the caps work as a nice applicator for pushing the epoxy into the cracks. I can't find it anymore. I have a crack in a cutting board to fill. I don't want 5 min cure times. Does anybody know where you can find the old Elmer's Epoxy? I also thought the amount in the small tubes was just right for filling cracks. I don't want to buy a large quantity.

[Allan Speers]

I am reading this thread with great interest as I am looking for the old Elmer's epoxy which had the blue and orange tops with white tubes. You had 24 hours for cure time. I used it to fill cracks in gun stocks and furniture. It was clear with a yellow brown tint and blended well. The little wide tabs on top of the caps work as a nice applicator for pushing the epoxy into the cracks. I can't find it anymore. I have a crack in a cutting board to fill. I don't want 5 min cure times. Does anybody know where you can find the old Elmer's Epoxy? I also thought the amount in the small tubes was just right for filling cracks. I don't want to buy a large quantity.

I've used that in the past & didn't like it. Much like "Ray-Crete," it sets up way too fast. Normally an epoxy with a 24 hr cure time also gives you more time to work, but these don't.

Sadly, most epoxies don't spec the "workable" time limit. It would be nice if they did.