Aloha,

It seemed to be time to focus the bits and pieces of info regarding epoxy into one place. For the most part, advice and reports of personal experience of various users have been pretty accurate. Nontechnical literature on the subject is scarce (to my knowledge) at best. In one of the few manuals, by System Three, they advise “learn by using”. (West System also has some instruction on their site.) So the info that I dispense here is mostly adapted from commercial/industrial, boating/marine, and the surfing industries. Adapt to your needs with a little common sense. Also, most of my sources are from the US West Coast and preservation supply houses.

In the beginning
About 40 years ago, I was making bamboo/brass bongs with epoxy. Two important points come with that admission – 1) I was successfully sticking dissimilar material together in the presence of moderate heat, and 2) that product, T-88 adhesive, is still on the market, albeit slightly modified. The advise here is to use a product with a good reputation. ( I ruined an expensive batch of teak spear guns breaking that rule.) I’ve been told by industrial chemists that there are few manufacturers of the base components. The endless variety of products come from manipulation of the basic recipe. The more closely you can understand the product and identify your need (like anything else), the better your choices.

Most folk know that epoxy is a two part system. A resin base and an amine hardener (A and B ). Notice that I did not say catalyst, because it is not. Catalyst set off reactions but are not part of the finished product, hardeners are. The rule here is – mix as thoroughly as possible (remembering how little time you have when using 5-minute stuff). Scrape the sides of the mixing cup and spatula. The amine hardener is designed to cozy up to a certain ratio of base, whether it is 1:1, 2:1, 4:1, 5:1 etc. They the link up to form the matrix. And, measure as accurately as possible. Disposable graduated cups work for me. Lab specimen cups are great. Trying to guesstimate by eye is chancy.

Types
Epoxy can be modified to do 3 main things – laminate (glue); fill or putty (fairing); sealants and coatings. There is some wiggle room between these categories. I guess part of the key is viscosity (and the manufacturers intended use). If you are gluing something porous, like wood, a less viscous (thin) product can be absorbed and result in a dry joint. If filling gaps, again on an absorbent surface, you can pre-wet the joint before filling. Or, if bonding hard surfaces and you want to roughen them up to create “scratch”, you may alter the viscosity to avoid surface air bubbles. The super fast types (5 minute) are convenient, but as Tom has pointed out, not as strong. Whether it’s because the epoxy does not have time to work into the surface to bond, or form a proper matrix, I don’t know. Besides, the longer set times give bubbles a chance to settle out.

Here is a shot of a carved church ornament showing – lamination of old to new; fill; sealing of new material.
Click to view attachment

As far as sealers go, there is only one product that I can recommend without reservation. That would be Smith's CPES. Besides its ability to work it’s way into various material, it has minimal “amine blush”. I’ll explain farther on.

There is one more specialty area to mention. That would be the jewelry industries products. I think Magnus mentioned the 220/330 family of epoxies. They have been around for a long time. Their use for attaching small, hard, precious materials together is ideal for inlays. Another one is Opticon. I used it to glue up opal layers with quartz caps. It might be ideal for metals or other non-absorbent materials. You do have to apply a little heat, but it dries optically clear and polishes to a glass finish.

Fillers
There are all kinds of materials that are or can be added to create a thixotropic (fancy word for thickened) mix. Most people use wood dust in the hope for a color match. Okay, but there are other ways. We use products like Thiksil, Q-cel, Aerosil, Microcell and glass bubbles to make our own fillers. The majority are silica based, not so good for carving. The manufacturers also have their own proprietary formulas. If you pick the right filler however, it’s consistency can come very close to wood (or whatever). Carving into the transition works well. Microcell is my choice, but I don’t know how available it is outside of the state. The next best thing is WoodEpox, from Abatron. They are a national company dealing in many restoration products.

Don’t forget that a ”filler” can be decorative. Crushed coral, malachite, shell, turquoise, jet, and metal flakes (to name just a few) are an option.

As to color, I’ll mention an alternative to the liquid colorants mentioned by others elsewhere. Bonded Materials, a commercial supplier of epoxies and cementaceous products carries the Davis Colors/Tru-Tone line. Their claim is to have 64 colors in powdered form. I’ve used several to good effect. Advantages are:
1) you can load up the powdered colorant to a certain state and not “go transparent” in a thinned layer;
2) you can achieve streaking to simulate wood to a certain degree (like Macassar Ebony) by preparing several colors at a time.
You might want to mortar and pestle the product to get a finer powder.

Reactions
Okay, so you made your selections and set everything up. Temperature will have the most effect on your work, with heat having the greatest. There are formulas for different climates. Epoxy gives off its own heat of reaction, so that contributed by the surroundings will only hasten the reaction. At first, you’ll see a drop in viscosity (thinning out) with extra heat, but the mix will soon start to gel. Maybe too soon. Three ways to extend pot life are:
1) chill the A/B component prior to mixing;
2) spread out the mix in a flat pan or dish (this dissipates the exothermic heat buildup of a concentrated mass);
3) apply mix in the evening when it’s usually cooler.
You can push the heat to speed reaction, but remember that with initial loss of viscosity things can start moving around and absorption into porous substrate can increase, causing bubbles. Needless to say, keep everything dry and try to work in an oxygen/nitrogen atmosphere.

The CPES is a different animal, as it has a two-tiered reaction rate. A mix in a capped bottle will resist setup for a day or so until opened and the solvent vaporizes. Then it can flash off in the sun in a matter of minutes.

Cleanup
If you’ve done your job, everything should be setting up nicely. As others have pointed out, as the epoxy goes from gel to solid, you can trim with sharp tools. Try not to be anxious as a drag cut can pull out your precious insert. Once hard, only abrasion will give controlled removal. Except those mixes with fillers that leave the solid semi-flexible. The WoodEpox and other carver’s putties from places like Woodcraft actually do that.

With scratch mixes, there is a surface residue commonly called “amine blush”. According to various sources, this is unreacted, excess hardener that migrates to the surface. Until you clean this off, nothing will stick over the epoxy. Fortunately, this is water soluble and can be scrubbed off with water. I would sand the cleaned surface to give “tooth” to the next layer. Once dried, only three things breakdown epoxy (heat will soften it):
1) strong bases (like sodium hydroxide, lye);
2) sunlight (UV);
3) mix of strong solvents like MEK, toluene, xylene (CPES has this and more).

Safety
Most of the hazard comes in the liquid phase. The hardener, in bulk, gives off ammonia like gases when first opened. Watch your ventilation. The second risk is contact dermatitis. This is usually reserved for high users (like me). Minimize contact and always clean up with soap and water, never solvents. Epoxy is water soluble. Solvents will only drive nasty chemicals into your skin.

As far as the CPES goes, the last line of the container says, “this product is inherently unsafe and cannot be made safe”. Use in well ventilated areas with respirator. Small amounts carry less risk.

And to finish off a rather wordy text is a picture of one of my favorite pieces. (Courtesy the INS Study Journal.) Check the list of diverse inlays.
Click to view attachment

If I have made any omissions or mistakes, please feel free to correct me.
And that’s all I know.

Karl

Thank you Karl!

Aloha Karl,

that's a pretty handy tutorial you've given us. I feel sure that there are loads of people out there for whom this sort of information will prove invaluable. Don't use glues much myself but I'll glean what I can anyway. Thanks very much. It's exactly this sort of effort on the part of our members that makes this place work as it does.

Namaste, Ford

Aloha Janel, Ford

You're quite welcome. This should only be the beginning. Tales of successes (and failures) are usually shared over cool beverages after work. Or with bleary eyes in the morning. I invite users to share their experiences. That is the best way to learn about epoxy.

Karl

Hi Karl,

This is an excellent intro to Epoxy and it's variations and possibilities.

One of the concerns with using epoxy with wood, when conserving old work, is that it can be a bit too stiff, and can cause damage to the surrounding wood as the wood moves with changes in relative humidity and the epoxy does not. I often use Epoxy heavily loaded with fairing compound (primarily phenolic micro-balloons) to create a lightweight filler for large areas. This technique was developed at the Canadian Conservation Institute, while I worked there, to fill in large areas of missing wood on outdoor sculptures (mainly totem poles). When Epoxy is loaded with a 1:1 mixture by weight it makes a very lightweight compound that can be pushed into areas of lost wood. It hardens in place, and provides a filler with similar expansion and contraction properties of the surrounding wood. In other words, when the wood moves with changes in relative humidity the epoxy based filler will move with it and not damage the wood. The filler can then be carved with standard carving tools, with simulated cracks, bore holes, and grain, and in-painted to match the surrounding material. I have seen huge areas in totem poles filled in so that the infills are barely visible, even up close.

I have also used this material to create very tough maquettes for casting bronze sculptures. It can be roughly sculpted in place over an armature and carved once it has hardened in great detail.

Just food for thought.

Phil

Aloha Phil,

Thanks for the comments. You got me. I took a couple of shortcuts on the post. First, I didn't transfer my earlier remarks in Materials>Bug control about the elasticity of CPES. To reiterate, cured residue in the mixing cup has the consistency of urethane. Somewhat like skateboard wheels. So I assume (and the manufacturer contends) that it gives the pocket or joint a flexible substrate. It's better than Abatron's LiquidWood, which cures like year-old Gummy bears.
Secondly, I drafted, then edited out, a section on the shape and geometry of fillers thinking I was going too technical. Silly me. Briefly, I was having problems with using glass bubbles on vertical surfaces (sagging), that I attributed to their shape (kind of like ball bearings). After going through some fairly exotic mixes using materials with more blocky, angular shapes that interlock, I settled on Microcell. It has about the same consistency as Abatron's WoodEpox; very light and fluffy ( like heavy marshmallows) and a lot cheaper. It sands and carves like spackle. The powdered pigments mix very easily into it.
I'm surprised at the resistance to cracking in those totems. As some woods can easily expand/contract 1/8th inch per foot, I would think a large diameter member could overcome any filler's modulus of elasticity. I had a problem once on a torii that I repaired.

btw - My supplier recently gave me a sample kit of S-1 Sealer by Industrial Formulators out of Burnaby,B.C. Ever try it? It is supposed to compare well to CPES.

Karl

Hi Karl,

My experience comes mostly from conservation of artifacts that are in a museum environment. There is a deep mistrust concerning epoxies among conservators, and many have very different opinions regarding their suitability. The main concern is that materials that are used when conseving an object should be reversible, regardless of what the material is, just in case you want to get the artifact back to whatever state it started in. I have seen some epoxy repairs done on wood where they caused more harm than good, but I have also seen some that were very appropriate, given the circumstances. Personally, I believe that epoxy is an excellent material, if used appropriately, but some conservators, perhaps irrationally sometimes, won't go near it for any reason.

I have never tried any of these products, but you have got me interested, particularly the flexible materials and the Microcell. Have you ever noticed any yellowing or hardening of the stuff over time?

When training as a conservator, I was taught to have a deep mistrust of any products that are pre-made, and that you always need to start with the basic materials and mix your own. When the microballoon filler was being developed, they tested the glass balloons, and found that they did work, but they preferred the phenolic because they were much easier on tools. My own trials with glass balloons proved this, and I have always stuck with just the basic mixture, only because I knew how it worked.

The expansion factor was a big factor in the tests, and it was found that the 1:1 mixture provided the right combination of elasticity and compression. By weight, this is a huge amount of filler, compared to the emount of epoxy. It is just really enough to hold the powder together. If the wood moved, the mixture was soft enough to allow for some compression, and it would crack before the wood if under tension, rather than cause damage. But these are under indoor conditions.

Phil

Aloha Phil,

We've got to stop meeting like this. I thoroughly understand how your experience as a trained conservationist influences your opinion of epoxy. It is by nature, not a reversible process. I do restoration work on exterior doors, windows, columns, korbels etc. Usually with a preservation architect looking over my shoulder.
We can discuss the merits of conservation versus preservation versus restoration off to the side before we get too esoteric. For the large majority of readers following this discussion, I'm guessing they are looking at ways to attach very small things to other vst. I suggest looking at the jewelry group; Opticon, 220, 330. They are all made by Hughes Associates, and have been on the market for decades. They are reliable enough to be sold by most of the major jewelry supply houses like Rio Grande, Alpha Supply, Kingsley-North and Gesswein, to name a few. If you know a jeweler or rockhound, ask him/her.

Karl

Phil,
From one conservator to another, I appreciate your cautionary words. I think especially pertinent is your comment about utilizing raw materials whenever possible, rather than proprietary mixes and formulations.
Though in the field of paper conservation we encounter the need for complex adhesive mixtures much less, there are examples aplenty in my area too.


-Doug

This informative discussion between conservators has been fascinating! There is much to consider when selecting a product to stick one part to another or as a filler. Once, I did a Google search and came up with hundreds of names for epoxy choices. Great dismay on my part, knowing little about it to begin with.

Some years ago, I wrote to a conservator with the Smithsonian Institution to inquire about what to use when I needed to place amber eyes onto wood. I needed something that would remain clear and not yellow or go cloudy. He gave me the name of a product from Epotek, the particular name is not in my mind right now. I'll provide that later when I go to the studio. It worked slowly, and did a nice job. I needed only drops of it though, and the company would only ship several ounces, way more than I could use in a life time of eyes. The shelf life was a problem. I had to purchase the expense adhesive parts every year. One of the parts would get crystals growing in it, which would melt upon heating, but would reform soon after. Once, it crystallized in the eye of the frog. Very disappointing and frustrating to use in the particular way I was trying to use it. I've moved on to another eye construction approach, needless to say.

Presently, I am using the hardware store variety epoxy, and cringe each time I reach for it, not knowing what might happen to it in the future. My purposes are for inlay of one material into another, non-porous to porous materials, woods, amber, antler, mammoth tusk, etc. What to select and where to find it have always been my stopping point, and I have not taken the step to acquire the right stuff. This thread is going to be helpful. Thanks guys!

Aloha Janel,

You bring up a very good point i.e. shelf life. As with most things (except fine spirits), fresher is better. It is usually the base resin that goes bad on me. (Although the hardeners on my basic formulations change color over time. I think they are absorbing water.)We here in the islands suffer from a double whammy. Shipping of hazmat designated materials has to be over water. It is hideously expensive or not available at all. My choices can be limited and pricey, hence all the experimenting. I have little parts of things stuck together scattered all over my backyard that I visit on occasion. Just to see what happens.

btw - I am not a trained professional like Phil and Doug; just a blue collar type of guy that is usually strapped to the side of a building with an architect yelling at him.

Karl

I get yelled at too!

Hi folks,

In spite of my cautionary use of epoxy in connection with older materials, I should note that I do in fact use it quite a bit in my own artwork. I just wanted to mention that I too learned quite a bit from Karl's expertise, and don't mean to cast aspersions on any of the information provided.

Good discussion!

Phil

Aloha Phil,

No worries mate. I learned a lot too.

Karl

Hello!

I am new to this site and new to carving and such as well. I have been working on a table which has been carved down as far as 1/2 inch into the table top. I will be staining the table as well. My question is this: will epoxy work to fill in the carved areas so that the table will have a flat surface with the rest of the uncarved table top, as well as preserving the stained color and the ability to see perfectly through to the bottom?

Thanks!

-Josh

This is fantastic as far as timing goes.

What brand/formula would you suggest for achieving a clear polish-able fill on some neat voids in a chunk of pink ivorywood?
Magnus sent me a piece with some natural voids that all connect to the surface. The voids aren't large, maybe a 1/4" deep and a few millimeters wide at most. I'd like to fill them with something clear if I can, so that they make little "windows" in the carving, but it needs to be something hard so that I can get a decent polish.
(I know it's possible, I've seen this done in bowls turned from heavily spalted woods.)

Thanks in advance,
LJ

LJ,

Cyanoacrylate, (or Super Glue in the US). At wood workers stores, you can purchase small and larger bottles of different viscosities, either for absorption from thin, or not flowing from a thicker variety. I have used this to fill a void. It polishes. I do not know how it reacts over time for clarity, color, or resistance to scratching. When you purchase this product, also purchase a spray can of the accelerator. Use it outdoors, as the fumes are not good for breathing. It smells bad too. A quick spray makes the glue set quickly. I do not know if it is a good idea to use the accelerator when applying layers to fill a void though, or for setting up a all at once fill, you will need to experiment.

I don't have enough experience with epoxy based compounds for what either of you are asking. Sorry.

Janel

I have just used Wikipedia, click here for a good read. Here is the particular excerpt:

Thin CA glue is also used as a wood finish, particularly among woodturners. Its fast drying time and glossy finish make it ideal for small applications which generally look best when glossy (such as pens), although it is messy and somewhat expensive. A common mistake made by novice users is to use an accelerator, which can cloud and thus ruin the finish.

Some climbers use glue to repair damage to the skin on their fingertips.

So, use the accelerator for attachments that will not be seen. And further down, you should really have a good read of this info:

Another important trait is that cyanoacrylate sets quickly, often in less than a minute. A normal bond reaches full strength in two hours and is waterproof. Accelerators such as toluidine trigger setting in two or three seconds, with some loss of strength.

Acetone, which is commonly found in nail polish remover, is a widely available solvent capable of softening cured cyanoacrylate. Nitromethane is also an excellent solvent. Methylene chloride is the most effective solvent, but is toxic. Gamma-butyrolactone is also effective at removing cured cyanoacrylate, and has low toxicity.

Low temperatures cause cured cyanoacrylate to become brittle. Cyanoacrylate's bonds can be weakened (allowing disassembly) by placing a glued object in a household freezer for several hours. Opened containers of cyanoacrylate glue can also be delayed from prematurely setting by storing the containers in the household refrigerator.

I'm just not sure that I can get this. I know that the standard superglue from walmart won't work, (I've tried filling with it before on a different project. It didn't stay put, and couldn't be polished) and "woodworking stores" aren't really available in my part of the US.
I am contemplating trying "Clear Epoxy 330".
According to what I found online:

* Versatile, quick drying adhesive
* Excellent for assembly of stones to metal findings
* Takes a high polish for inlay.
* Clear in color. Thickens in 15 minutes.

Sounds like it might work, and Rio Grande has it. I could also use it for other stuff.

Thoughts?
LJ

I've seen acrylic resin used for this exact thing before. You might talk to a taxidermist about the material they do water with, for fish mounts.

LJ

Ooo, good ideas!

Hi all,

I'm not a carver but I am an engineer researching epoxy formulations for machine tool parts as a hobby project. I saw your discussions of the Hughes Associates Attack Product on which I was trying to find manufacturer information so I figured I'd share some of what I'd learned from other folks who have taught me.

Epoxies and hardeners are water reactive and also air reactive with Carbon Dioxide. The reaction with carbon dioxide is the formation of carbamates. The carbamate reaction can be prevented by purging the storage container with dry nitrogen or argon gas before resealing it. Also, one must make sure that the bottles are sealed tightly after use and if purged sealed tightly after purging. It's preferable to handle epoxy for use in an area that does not have gas or kerosene heat due to CO2 and it is preferable to do epoxy work with as low a relative humidity as possible.

The shelf life of most resins is something like 6 months or a year maybe two. If kept at too low a temperature, they will crystallize and sometimes the chemical properties of the crystallized versions are not the same as the liquids. To get rid of the crystals, heat the epoxies and hardeners gently to about 100F and wait for all of the crystals to melt. Don't use the crystalized stuff without melting the crystals as it may behave badly and ruin parts. To prevent the crystallization, one wants to store the material at room temperature or a bit below but some of the hardeners I work with crystalize in the high 50's or 60's Farenheit.

The best results for epoxy are obtained after the dissolved air is removed from the mixed epoxy by a few minutes in a vacuum chamber. The properties of cured epoxies are also highly dependent on the temperature at which the cure occurred. The speed of cure is also very strongly affected by increased temperature. Slower cured epoxies are usually tougher than very quickly cured epoxies.

Welcome to the forum ckelloug, and thank you for your expertise on this subject. There is so much to be learned! Thank you for sharing.

Janel