centershot
Silver $$ Contributor
The first job that I did worked fine. Now, this latest bedding job will not harden. Anyone else have an issue with this? Is there anything I can do to firm it up? Mixed it 3 to 1.
Devcon Not Hardening
- Thread starter centershot
- Start date
Jay Christopherson
Not An Admin
3:1 by what? The instructions say 9:1 by weight and 2.5:1 by volume. Either way, 3:1 is off. My (swag) guess is the mix ratio is off and it's not going to harden properly. Cold temps can cause slow cure times as well, but I still think your mix ratio is off.
You might be able to just let it sit and eventually mill or remove the bulk of it so you can re-bed it... been there, it's frustrating, but not too bad.
Last edited:
If you're using Devcon 10110 the ratio is 9 to 1 by weight, 2 1/2 to 1 by volume.
If it's another epoxy, could it be out of date? If you have multiple kinds of epoxies on the shelf, could be the wrong hardener. Nothing to do now but tear it out. Should be easy.
Generally, high performance epoxies have a mix error tolerance of about 5%. They're not like polyesters where you can vary the catalyst to the temperature and conditions. So I alway use a gram scale to proportion epoxy by weight. For bedding, a 20 or so gram batch is about right.
Often, you can add heat during cure to help it along, especially if working in cold shop and parts are cold during assy. A cardboard box with slots cut in each end for the action/stock to sit in creating a box around the bedded area. Cut a round hole in one end and stuff a hair dryer ( NOT a heat gun) into it so it fits tight, and cut a exit hole slightly larger in the other end. This will keep the work at 170 degrees or so for cure. Devcon 10110 will cure solid enough to pop out the action after about 2 1/2 hours using this method.
If it's another epoxy, could it be out of date? If you have multiple kinds of epoxies on the shelf, could be the wrong hardener. Nothing to do now but tear it out. Should be easy.
Generally, high performance epoxies have a mix error tolerance of about 5%. They're not like polyesters where you can vary the catalyst to the temperature and conditions. So I alway use a gram scale to proportion epoxy by weight. For bedding, a 20 or so gram batch is about right.
Often, you can add heat during cure to help it along, especially if working in cold shop and parts are cold during assy. A cardboard box with slots cut in each end for the action/stock to sit in creating a box around the bedded area. Cut a round hole in one end and stuff a hair dryer ( NOT a heat gun) into it so it fits tight, and cut a exit hole slightly larger in the other end. This will keep the work at 170 degrees or so for cure. Devcon 10110 will cure solid enough to pop out the action after about 2 1/2 hours using this method.
The correct mix ratio is 9:1 and no, there is nothing you can do now except perhaps scrape it out and start over.
Outrider27
Gold $$ Contributor
And a little heat, as has also been mentioned above. But don't be discouraged if you end up tearing it out and starting over. Stuff happens, and sometimes we never are able to figure out what went wrong, but at least this is one that can be dealt with by a re-do.
Fast14riot
Gold $$ Contributor
Yeah, epoxies are very dependant on proper mix ratios to cure properly. Polyester resins have much more latitude. Basically, grind/scrape/gouge the epoxy out. It ain't gonna do what epoxy do. No matter what heat nor time you apply to it, it's not going to be stable.
centershot
Silver $$ Contributor
This was by volume.
timeout
Silver $$ Contributor
I'm confident that you added too much of the activator. Devcon will not harden if too much hardener is added. It's one of those things that defies the adage "if a little is good, more is better". Devcon also has a very long shelf life. I weigh it on a powder scale when mixing. I first weigh the putty. Take that weight times 1.111111. Add the white activator until you achieve the exact number as a result of the multiplication. I promise you the Devcon will harden properly.
You're correct. Nor will it achieve the desired properties if too little hardener is used. Polyester resins and epoxies are two entirely different animals.
Polyester has long molecules which naturally want to bond together. Think of polyester as a bowl of spaghetti which, if left long enough, will bond wherever the noodles cross one another and form a big hard blob.
Polyester molecules are prevented from bonding by a chemical inhibitor. Mixing in a small amount of special catylist simply removes the ability of the inhibitor to prevent bonding. The catylist doesn't play a significant part in the final cured product. More catylist will produce a quicker cure. A solvent, nearly always styrene, is used to reduce the viscosity so that it can be used for laminating fiberglass cloth.
Epoxy products are entirely different kettle of fish. Typically they don't contain solvents. They usually consist of two parts, A and B. Think of Epoxy as baloney sandwiches. If the idea is to make sandwiches , you need two pieces of bread (part A sometimes called the resin) and one piece of baloney (part B sometimes called the hardener) for each sandwich. You'll start with 1000 pieces of bread and exactly 500 slices of baloney. Done properly (similar to mixing epoxy properly) you'll have 500 sandwiches.
If you don't have the right number of bread or baloney slices, you'll either not have enough sandwiches or you'll have left over components which are NOT sandwiches and the gourmet banquet you had planned for your red-neck friends will be ruined.
Similarly, if you use too much or too little hardener when making epoxy, there will be left over components (either A or B) which are NOT epoxy; therefore, the mechanical properties of the final product will be compromised.
Goofy analogy, but you get the point.
Liven The Dream
Gold $$ Contributor
heat Lamp will help set up time ?
centershot
Silver $$ Contributor
Thanks for the come backs. I did use too much hardener. I have scraped it all out. Fun job. Is there a solvent to wipe away the residue?
chuckshooter
Silver $$ Contributor
acetone
XTR
F-TR obssessed shooting junkie
I've always used isopropyl alcohol for cleanup on q-tips and paper towels when I was doing bedding to clean up the stuff that oozes out, not sure if it's the best thing for cleaning out the inlet though.
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