Introduction: Using Epoxy and Dye to Fill Knots and Cracks in Wood
When doing wood working projects, sometimes using wood with knots and cracks is necessary because it is all you have to use or sometimes is desired to give a piece character. In the cases where you need a surface to be flat and functional (as with a table) but maintain the look, you can fill cracks with epoxy. This instructable will show you how easy it is do this.
The example wood I am using is knotty alder. This is for a kitchen table build I am doing.
Check out the YouTube Video I made of this project: https://youtu.be/vWh2bXLjwyI
Devcon Epoxy - http://amzn.to/2tH7Q7N
Rit Black Dye - http://amzn.to/2uK8Uqd
Blue Painters Tape - http://amzn.to/2haDBll
Ridgid Random Orbital Sander (or any other sander) - http://amzn.to/2uG4UZu
Plastic Cup or something to mix epoxy in
Plastic spoon\knife or something to apply epoxy (best if disposable since epoxy don't clean off well)
Step 1: Prep Work and Mix Epoxy and Dye
It is best to prep your project by taping off each knot/crack you plan to fill as the first step in the process. This is because most epoxy products have a fast cure time (I used 30min - 1hr epoxy) and will not allow you the time to prep your work area after the epoxy is mixed together.
I used Rit dye, which can be bought one amazon, local walmart or in my case local grocery store. Simply mix with water. I wasn't measuring the amount used as there is lots of room for error. Basically, I added dye to water, gradually adding more until the water was the color I wanted.
I used Dev con 2-ton epoxy which has a 30 min cure time. Mixing epoxy is pretty straight forward. I don't suggest using 1 min or 5 min epoxy as the time it takes to mix everything together and apply it to your project is typically longer than those curing times.
Mixing the Dye with Epoxy
Now that both the epoxy and dye are each mixed separately, it is time to combine the mixtures. What i did was take a plastic teaspoon and added 3 teaspoons of black dye to a whole bottle of epoxy. Then stirred it together. I was happy with the mixture. My suggestion is to use enough to get the color you want, but also the consistency. You don't want it to be too watery.
Now on to applying it to your project
Step 2: Fill Knots/Cracks
Now the easy part.... maybe
Fill each knot or crack - pretty straight forward right? yes, but here are some considerations:
1. Make sure you tape off the backside. It is common for knots/cracks to go all the way through to the other side of the work. If you don't tape it off, the epoxy will just fall through and you will not like the result.
2. After you fill the knot, wait 5 min and then come back to top-off the knot/crack, sometimes you think you put enough in, but gravity will prove you wrong.
3. Consider timing: If using 30min/1hr epoxy, the handling time is about 20 min before it starts to get harden up (atleast my experience in my conditions (hot AZ garage), so plan your application ahead time. If you are doing a big project, don't mix all the epoxy at the beginning. Maybe break the application into 2 phases.
4. Don't try to be too perfect with application. If anything error on the side of putting on too much epoxy. It sands easily with a random orbital sander and 80 grit sandpaper. It might save you time, to put on too much and spend a little extra time sanding vs. not enough and have to go through mixing another batch of epoxy and also having to spend as much time sanding anyway.
Step 3: Remove Tape and Sand
In this simple step, just remove the tape. If some gets stuck under the epoxy, don't worry about it and move on to the next step. The sanding step will take care of it.
Like true with most projects, the right tool can make this very easy and lack of tools doesn't mean you can't do it, but you need to put in more effort. Using a random orbital sander makes really quick work of this step. Be careful not to sand in one place too long, you don't want to ruin your piece by not moving the sander. Do you best to keep it nice and even and only removing the high-spots.
Once you sand off all the excess epoxy you are DONE!
Now you can go on to the next steps in finishing your project. I have attached a few photos of some fully finished projects that I used this exact method on.
Be sure to check out the video I posted of this project on here and subscribe to keep up with future projects: https://youtu.be/vWh2bXLjwyI