PDA

View Full Version : Thinning epoxy



radkins
10-29-2013, 09:33 PM
Is it possible to thin epoxy glue without ruining it's strength? What I need to do is repair some cracks in wood but unless I can get the epoxy thinned, and I mean really thin, I think it will just lay on the surface and do no good, any suggestions? How about suggestions on other methods of repairing these cracks? Appearance is very important since this is a repair in a non critical area of a walnut gunstock, actually the two cracks would probably not be a problem unless they continue to grow but they are a real eyesore!

PStechPaul
10-29-2013, 09:42 PM
I have found that epoxy will get more "runny" when heated with a heat gun, but it will also cure faster, so you might need a slow setting type. Try it on a piece of scrap wood first. Also check out some industrial epoxy sources for detailed information on properties. You can even get samples if you present yourself as a company. Here's one I have used: http://www.epoxies.com/

gizmo2
10-29-2013, 09:44 PM
Toluene does the trick, and the epoxy works the same. Trouble is, last time I ran out (of toluene) I couldn't find any in town. I didn't check everywhere, just the big box hardware joints.

lakeside53
10-29-2013, 09:50 PM
Get some marine epoxy that's designed for wood. I have some that's really thin and doesn't even "gell" for several hours. It wicks into tiny spaces and the surrounding wood fibers, and takes about a week to fully cure at 70F. On mahogany, walnut and other medium to dark wood, it's close to invisible. Hopefully you haven't oiled the gunstock cracks.


If you intend on "thinning" do contact the manf. Any other advice is interesting, but...

elf
10-29-2013, 09:50 PM
There are low viscosity epoxies available like Git Rot that would probably be better than thinning.

PStechPaul
10-29-2013, 09:53 PM
I found what seems to be a good article about thinning epoxy with solvent or heat, and particularly for use on wood:
http://www.seqair.com/skunkworks/Glues/WestSystem/Thinning/Thinning.html

JCHannum
10-29-2013, 10:18 PM
Depending on depth and location of the crack, consider using crazy glue instead of epoxy. It is often used in these types of repair. It will penetrate the grain of the wood and stabilize it as well as provide a strong repair.

A several applications might be necessary as the first few serve to seal the wood. Additional applications will join the wood. It has the additional advantage of matching the wood and often makes the repair invisible or very difficult to detect.

Allow several hours between applications for the glue to set.

darryl
10-29-2013, 10:27 PM
If you use crazy glue, use a good one- not the dollar store stuff.

caveBob
10-29-2013, 10:46 PM
...How about suggestions on other methods of repairing these cracks?...

Google "stabilized wood". Basically, it's impregnating/saturating the cells with acrylic drawn in via vacuum/pressure. One outfit that gives prices: http://www.stabilizedwood.com/

portlandRon
10-30-2013, 01:43 AM
You can use Acetone to thin epoxy and it will have little effect on the strength. Don't go over 5% by volume.
Like stated above if you want it real thin get some Git-Rot from some place like West Marine but it is expensive.

Ian B
10-30-2013, 04:29 AM
It sounds like the OP is trying to fill a couple of cracks in the wood for cosmetic reasons, rather than for strength. To get the epoxy into the crack, try pre-heating the wood. The epoxy will become less viscous when it's applied, and a bit of scraping back & forth across the cracks with a squeegee should see enough go in.

Ian

beanbag
10-30-2013, 04:51 AM
http://www.captaintolley.com/

jep24601
10-30-2013, 08:10 AM
Methyl methacrylate formulated as a low viscosity crack penetrant is a good product. May be available from a builders supply house.

radkins
10-30-2013, 08:16 AM
Thanks everyone lots to consider here and I will check out all these suggestions, up until now I was in a real pickle as to what to do about this. These cracks are in a very highly figured piece of burl walnut and the cracks are shrinkage cracks in the grain, they are quite visible but barely open at all and in fact would not be much of a problem if the finish would not crack over them (it would if I just leave them). This piece of wood is far to valuable to just toss in the trash and it has air dried for over 25 years so I doubt the cracks would get any worse as long as they are not stressed, when I get back to the shop today I will try to get some pics of this thing so that what I am trying to fix might become a bit more clear, thanks again everyone you have given me some things to consider so that I can do this right.

radkins
10-30-2013, 11:05 AM
Well the pics didn't work, can't tell the difference between the cracks and the wood grain!

JCHannum
10-30-2013, 11:45 AM
If the aim is to repair shrinkage cracks, not cracks from damage or mishandling, I would and have used crazy glue. A product that has been in use for a few centuries for similar repairs is stick shellac. It comes in a variety of colors to match the surrounding wood and is applied with a hot knife. Brownells carries it as probably do artist, and furniture restoration suppliers.

I suggest that, prior to attempting any repairs, you rough the blank to near final shape as what is on the surface might not represent what is beneath it.

Paul Alciatore
10-30-2013, 12:01 PM
I have done a little wood work. You do not say anything about the finish on the wood: stain, paint, oil, or what? I would carefully consider that finish because things like epoxy will not take a stain or a rubbed oil finish.

If the intention is to just fill the cracks, why are you using a glue? There are wood fillers that would also allow almost any type of finish to be applied and they are easier to thin.

If you do need some additional strength, then perhaps a good wood glue, which can be thinned with water, can be used. A water based glue would easily penetrate the cracks. Most wood glues are stronger than the wood being glued.

elf
10-30-2013, 12:33 PM
I use CA a lot in my woodturnings and it will work for this. However, you may need to apply it to the entire piece in order to keep the finish even. Most hobby stores will carry good quality CA in 8 oz. or larger sizes.

You can use sawdust mixed in with the CA to help disguise the glue lines. Practice a bit first on a scrap piece.

CA is an excellent finish by itself. It will polish to a high gloss. Oil finishes will not work well with either epoxy or CA.

Dr Stan
10-30-2013, 01:39 PM
Have you considered Gorilla Glue?

Jono
10-30-2013, 02:42 PM
Have you considered Gorilla Glue?

You need to consider longevity. Nearly all commonly available epoxies and urethanes go yellow over time and especially with exposure to light. Even a top quality surfboard spec epoxy will yellow eventually, though later by far than a cheap one. There are inherently non yellowing resins (eg aliphatic) but I don't know of any commonly available.

If you don't need the strength of a modern resin I'd totally agree with those posts re traditional gunmaker's recipes. There's an interesting you tube about Purdey's- they take over a month just to varnish a stock.

radkins
10-30-2013, 03:11 PM
This wood is just a blank at this point and when I roughed it out I was hoping the cracks would work out but unfortunately that's not going to happen, there is only a small amount of wood left to be removed and the cracks are obviously going to persist.

lakeside53
10-30-2013, 03:50 PM
I know the type of fine cracks in burl walnut you are referring to. If it was mine I would coat the entire surface with the wicking marine epoxy, then sand off. Test a separate piece if you are concerned. The fine cracks will be invisible after you apply any finish.

strokersix
10-30-2013, 04:20 PM
Can you apply epoxy, draw a vacuum around the part to suck the air out of the cracks, then relieve the vacuum to push the epoxy into the cracks?

CarlByrns
10-30-2013, 05:02 PM
Contact these folks: www.westsystem.com/ss/ they are the experts on wood, epoxy, and wood repair. If they can't help you, no one can.

dian
10-30-2013, 05:16 PM
the advantage of epoxy is that it has no volatile solvents in it, so it doesnt shrink. you can thin it with acetone, but but how will that get out of the crack to make the resin harden? its true, that most epoxies go yellow, if exposed to sunlight. it seems "west system" 105/207 stays clear, as it is used for tabletops. the thinest epoxies are for injecting concrete, but i doubt if they stay clear. dont thin epoxies.

if you want to get fancy, look into the systems used to repair windshields. they cure by ultraviolet ligh.

firbikrhd1
10-30-2013, 08:47 PM
I have used a product similar to Git Rot called Stop Rot made by Fasco
http://www.fascoepoxies.com/products.html
It works very well, the wood soaks it up like it would oil or water, then when hard it makes it impervious to water and a great deal tougher. The dryer and more porous the wood the better.

ed_h
10-30-2013, 09:10 PM
I've used both the West system and the thin epoxies formulated to wick into wood, as noted above. One trick for these or other fillers is to use a syringe with an appropriately sized tip to inject the material deep within the crack. I use industrial syringes, but have also acquired them from a pharmacy (if you know them) or a veterinarian.

radkins
10-31-2013, 07:48 AM
I have syringes with very thin needles (from the vet for our cat with a chronic kidney problem) and I wondered about trying to inject the epoxy, actually that's the real reason I wanted to thin this stuff. From searching the links you guys have provided I see there are epoxies out there that are tailor made for what I need to do and I had no idea these were avaliable, I will try both epoxy and wood glue on some of the scrap pieces before I attempt the stock blank.

As usual here I am learning a heck of a lot more than I started out seeking, thanks everyone for the help!

TGriffin
10-31-2013, 08:21 AM
I've done a lot of research on epoxies at the company I work for. We found that ordinary alcohol (ethyl) will thin epoxy to any viscosity needed without affecting its strength. The alcohol completely evaporates leaving the epoxy behind to cure normally.

Tom

kc5ezc
10-31-2013, 12:00 PM
Try Sherwin-Williams or another paint store. They even have it here in rural Oklahoma.

dian
10-31-2013, 12:53 PM
[QUOTE=TGriffin;882869]I've done a lot of research on epoxies at the company I work for. We found that ordinary alcohol (ethyl) will thin epoxy to any viscosity needed without affecting its strength. The alcohol completely evaporates leaving the epoxy behind to cure normally.

that is hard to understand. it might work on a thin film, just as solvent evaporates from paint. but if you pour it into a cavity, the resin will start hardening while the alcohol evaporates leading to shrinking and porosity. it would seem that alsohol is a very bad solvent, because it will intoduce moisture into the epoxy on top of that. if it were that easy, you could thin ordinary construction epoxy with acetone and inject it into contrete, instead of using the expensive low viscosity stuff, right?

since you seem to be knoledgable on the subject, can you please explain?

TGriffin
10-31-2013, 01:29 PM
[QUOTE=TGriffin;882869]I've done a lot of research on epoxies at the company I work for. We found that ordinary alcohol (ethyl) will thin epoxy to any viscosity needed without affecting its strength. The alcohol completely evaporates leaving the epoxy behind to cure normally.

that is hard to understand. it might work on a thin film, just as solvent evaporates from paint. but if you pour it into a cavity, the resin will start hardening while the alcohol evaporates leading to shrinking and porosity. it would seem that alsohol is a very bad solvent, because it will intoduce moisture into the epoxy on top of that. if it were that easy, you could thin ordinary construction epoxy with acetone and inject it into contrete, instead of using the expensive low viscosity stuff, right?

since you seem to be knoledgable on the subject, can you please explain?

I can't explain the mechanics behind it, but it was a Locktite engineer who recommended using alcohol as a solvent. The alcohol apparently thins the epoxy without affecting the curing process. I suspect that the alcohol is gone before the cure starts due to the cooling effect of the evaporation. Using acetone in construction adhesive is not the same thing because construction adhesive relies on solvent evaporation for the cure, not a catalyst. The OP is looking to use it as a thin film anyway, so it should work fine.

Tom

ckelloug
10-31-2013, 01:44 PM
Isopropyl Alcohol, Toluene, and Acetone will all thin uncured epoxy. None of them do so without compromising the strength however so in this respect TGriffin is not correct. For a given application, the deleterious properties of the dilutant may be small enough not to compromise the particular application but that is a very different statement than saying it has no effect.

In paint like applications where the strength is not too much of a concern and performance is acceptable, solvent borne epoxies are used. Toluene seems to be the most common solvent in the formulations I've examined but YMMV.

In the 21st century, a standard di-functional resin with viscosity like honey [Diglycidyl Ether of Bisphenol A epoxy (DGEBA)] is thinned with what is called a reactive dilutant. A reactive dilutant is generally an epoxy mono-functional molecule with much lower viscosity that participates in the curing reaction (Examples would be C12-C14 glycidyl ether and cresyl glycidyl ether). Another common reactive dilutant is nonylphenol which does not have an epoxy ring attached. In general a reactive dilutant is preferable to a non-reactive dilutant for reasons of shrinkage, chemical resistance and strength. Even reactive dilutants negatively affect strength so there is a balancing act betweeen viscosity and strength/chemical resistance when designing thin epoxies.

Unless thinning the epoxy is part of a need to do-it-ones-self, better results are likely to be had by buying an epoxy and hardener suited to a given project. Unfortunately, buying the right epoxy is not usually something you can do at the hardware store.
One source of epoxies that has enough kinds to satisfy most users is uscomposites.com. Their #635 resin is very thin and can be had with a variety of hardeners depending on the open time required. Also, if you know exactly what you need, sometimes it is possible to buy industrial samples from Huntsman.

M.Barry
10-31-2013, 02:23 PM
If the crack goes through the wood, put a vacuum nozzle on the opposite side to suck the glue into the crack.
M.Barry

michigan doug
10-31-2013, 02:29 PM
Low viscosity cyano aka "crazy glue" works very well for this application. This is widely available at hobby shops that cater to the remote control people. Also widely available online.

Wicks into cracks beautifully. May require a couple of applications to totally fill the crack. You can also just drip a little into the crack, and let that set up for a day. Then make some sawdust from the same stick, pack that in the crack and then soak it with the same "water thin" cyano. Near invisible repair.

Wear gloves, use good ventilation.

I've had good luck with Bob's stuff, but there are many others:

http://www.ebay.com/itm/Bob-Smith-Industries-CA-Cyanoacrylate-Adhesive-Glue-Thin-Medium-Thick-/111190310874?pt=LH_DefaultDomain_0&var=&hash=item19e3757fda



Keep us posted.

doug

Mike Burch
10-31-2013, 06:11 PM
If you want to thin epoxy, why not just use epoxy thinners? Or am I missing something here?
Any decent marine shop (chandlery) will sell epoxy and the matching thinners.
International Paints make a product called Everdure which is a very thin epoxy designed to be applied wet-on-wet to seal boat timbers. Like many epoxies it does leave an amine blush on the surface when cured, a thin film which has to be removed by sanding before any further coats of finish are applied.

dian
11-01-2013, 02:09 PM
Isopropyl Alcohol, Toluene, and Acetone will all thin uncured epoxy. None of them do so without compromising the strength however so in this respect TGriffin is not correct. For a given application, the deleterious properties of the dilutant may be small enough not to compromise the particular application but that is a very different statement than saying it has no effect.

In paint like applications where the strength is not too much of a concern and performance is acceptable, solvent borne epoxies are used. Toluene seems to be the most common solvent in the formulations I've examined but YMMV.

In the 21st century, a standard di-functional resin with viscosity like honey [Diglycidyl Ether of Bisphenol A epoxy (DGEBA)] is thinned with what is called a reactive dilutant. A reactive dilutant is generally an epoxy mono-functional molecule with much lower viscosity that participates in the curing reaction (Examples would be C12-C14 glycidyl ether and cresyl glycidyl ether). Another common reactive dilutant is nonylphenol which does not have an epoxy ring attached. In general a reactive dilutant is preferable to a non-reactive dilutant for reasons of shrinkage, chemical resistance and strength. Even reactive dilutants negatively affect strength so there is a balancing act betweeen viscosity and strength/chemical resistance when designing thin epoxies.

Unless thinning the epoxy is part of a need to do-it-ones-self, better results are likely to be had by buying an epoxy and hardener suited to a given project. Unfortunately, buying the right epoxy is not usually something you can do at the hardware store.
One source of epoxies that has enough kinds to satisfy most users is uscomposites.com. Their #635 resin is very thin and can be had with a variety of hardeners depending on the open time required. Also, if you know exactly what you need, sometimes it is possible to buy industrial samples from Huntsman.

thanks for that.

radkins
11-03-2013, 07:22 PM
Been doing some experimenting with the scrap from this blank, I have acquired some Loctite brand epoxy and also some thin super glue plus some carpenters strength wood glue. I thinned two batches of epoxy, one with alcohol and one with lacquer thinner, and both seem to wick into tight cracks pretty good but I also butted some ends together and glued them with both concoctions so that I can test the strength. The wood glue was REALLY thick so I diluted it 50/50 with water and that gave it the consistency of water, while it did soak into the wood fairly well it did not seem to want to wick into the cracks. I then added a tiny amount of Dawn dish washing liquid and the cracks then literally sucked the thinned glue into them! While all this might seem to be a bit of over-kill I have run into this problem in the past and expect to again so if I can determine the best method it may make it easier in the future, besides you guys gave me a lot to consider and to work with!


I wonder if the dish detergent will degrade the carpenter's glue? I only used about two drops in about 3 to 4 ounces of 50/50 water/glue mix but it made an amazing difference in the way the mix was wicked into the cracks.

elf
11-04-2013, 01:00 AM
I think the true test will be how each affects the finish. Have you decided what finish to use?

radkins
11-04-2013, 06:54 AM
I will probably use a Urethane finish, that's what I normally use because it's easy to work with and dries fast plus it's tough as nails once it's dry.


Well it looks as if the dish detergent and glue do not get along too well! Just returned from the shop this morning and the test pieces that were joined with the 50-50 glue/water mix seemed to hold nearly as well as the undiluted glue, the bond may very well be weaker but it penetrated deeper into the joint (I used the joint in a manner to simulate a crack when applying the glue). The joint that had the detergent mixed into the glue/water penetrated MUCH better than the glue without detergent reaching 100% of the surface as opposed to about 75% without but it didn't have near the strength and easily broke so I guess that won't work!


Another question, I have had several people tell me that super glue is not permanent and will lose it's strength in about two years???????? I bought the super glue (Loctite brand) and intend on testing it also but if it's not going to last for long it might not be a good option, any truth to the relatively short lifespan of this stuff?

vincemulhollon
11-04-2013, 07:30 AM
Another question, I have had several people tell me that super glue is not permanent and will lose it's strength in about two years

Pure urban legend. Nothing to do with time at all. You can set some CA and if you abuse it 24 hours later it'll crack just as well as the urban legend claim of 2 years.

CA is very brittle at room temps and super brittle when cold (like in a freezer or outside up north). Its the only thing I can think of at this time of the morning where if you are trying to break a bond putting it in the freezer or dry ice works nearly as well as hitting it with a torch (outside due to fumes)

I bet there is a very specific app where 2 years of abuse is precisely correct to crack a bond, therefore "all CA fails in exactly two years in all applications everywhere".

Probably the failure mode relates to gluing wood, then in the winter when its colder and lower humidity and lots of shrinking wood if it fails because that's not a good app for CA the user will claim they just didn't use enough, but if it takes a complete cycle to fail, then next winter when it fails its because CA has a little calendar in it that counts off 24 months or something.

Bob Ford
11-04-2013, 09:37 AM
Radkins,

It is a little late. http://woodworker.com/c-Finishes/fillers/

Bob

michigan doug
11-04-2013, 04:13 PM
I have rc airplanes that are 20+ years old that were assembled with cyano adhesives exclusively. Still holding up well.

The cheap generic cyano products are not nearly as strong as the stuff made for modelers. I would trust the name brand stuff though, like permatex and locktite.


doug

SGW
11-04-2013, 04:36 PM
Have you considered Gorilla Glue?


I hope you're not serious.

lakeside53
11-04-2013, 08:16 PM
Yep, my thought also - the worst type - foams (curing action in the presence of moisture) and doesn't like to penetrate.

boslab
11-05-2013, 01:50 AM
There was a guy from a contractor in work that used to do maintenance on sample carriers for an air powered system like in hospitals, he used to heat the carriers (ali) on a hotplate and apply the glue, it turned from gloop to piss when hot, the glue was araldite 2021.
Disadvantage was the smell of popcorn!
Mark