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Poliester resin impregnation in porous woods - Tutorial

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There are many beautiful woods that are too soft and porous to be used on knife handles.


If you still use them, when you finish the piece and polish the handles with rotative polishing cloth and polishing paste, you fill all the porous with the paste, leaving a dirty and matte look.


With this method I'm about to describe, it's fairly easy to get a nice finish and a decent hardness. For this I use a Vacuum pump (what can be seen on the pictures is an old refrigeration system with a vacuometer connected to it - it marks 22.5 inches).


The idea is to impregnate all the empty spaces of the wood with the polyester resin.



Piece of nut tree root





Making a hole on it like I was going to use it for a hidden tang blade.





Threading it.





I screw a threaded accesorie to allow me to fix a piece of hose. This hose ought to be transparent/translucent so we can check when the resin starts to get into it and cut the process before it reachs the pump.





Placing 50 grams of polyester resin (is important that it's as liquified as posible) on a plastic bag similar in size to the piece of wood to later place the wood inside it.







Once the wood is placed inside the bag with the resin, I seal it with pvc tape and start the vacuum pump.







When the resin starts to harden, I turn the pump off.





These are the wood piece from the process and another a little bit bigger after sanding with a 400 grit and polishing them with a rotative polishing disk with polishing paste.







On this picture you can see an inner crack on the root, completely sealed with the resin.





And finally, here you can apreciate the good polishing this wood takes after this process.






As always, questions welcomed!


Thanks for looking!



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Very cool idea! What is the average time period for a piece to get completely saturated? I have alot of spalted maple that is close to balsa wood in softness and I will have to try this. I have a couple compressors/vacuum pumps that should work great, they even have the mm/hg guages on them.


Thanks for posting the tutorial!

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Below are all the question I got from the forums answered to my best knowledge.


I keep getting A LOT of questions about the resin, times, etc, but those depend on LOTS of factors that vary from resin to resin, depending on manufacturer and type of resin. Locally I have access to thick, medium thickness and more liquified resin, and that's pretty much it, the only difference resides on the ammount of liquifier (styrene monomer) that has been included in the mix.


If I buy the thick one that comes with 2% and I add 8% more in my shop, I get the same liquified resin as if I'd gotten the liquified one (that has the maximum of 10% of SM)


My advice is to ask ALL this questions to the seller or manufacturer of the resin you have access to, as, again, this is just my experience.


And regarding that fact, I'm not trying to sell anything here, I'm just posting what works for me on my shop, with the materials I have access to. What I post in these tutorials is simple stuff that actually works for me, I'm not making theories about it. But with any other shop related stuff, you will have to find your own way to make it, trying and changing some variables in the process :)


I will help anyone with questions, but please don't think that you will do exactly as I do on the pictures and get the exact same result on the first try. Maybe you do, maybe you don't, but don't feel bad if you don't succeed at first, it's all part of the game.


I don't mean to sound condescending or like I'm hiding stuff here (I can assure you neither is the case) but just wanted to say this as this is not an exact science, and if some folks try it and don't succeed at first, I don't want them to be dissapointed or think that I skipped some steps to "hide the secret" or anything like that :)



That wood is beautiful, I take it that it is a native plant/tree to your area?

Nah, I don't know where walnut is originally from, though this root came from one of our Northern states (provinces)



What is that pump you are using?

It's a compressor of a regular (house) refrigerator. I just connected it on the proper end :D



What does one use to thin epoxy type resins ? Or are they all different?

It is NOT epoxy resin. It's Polyester resin, as it's more liquid than the epoxy one. Epoxy doesn't get liquified enough (at least with the epoxy resins I have access locally)



How deep does the resin penetrate? How does this work if you want to dye the wood? The box elder is basically white. I've been dyeing it with brown leather dye. I wouldn't think the wood would absorb the dye after being "resinated". Would it?

It gets COMPLETELY saturated, and you're right, you wouldn't be able to dye it after this process. However, you can add dye to the resin and get it dye on the same process. I just don't know how it would exactly look though.



Looks like a neat idea but I would question how effective it is.

1. How far is the hole drilled down the wood?

2. I would think that a shallow hole would not have a lot of vacuum in the lower end of the block.

3. Does this work only for a hidden tang knife? Do you have to have a large block for scales so you can cut them off?

4. Have you ever sliced the wood crossgrain from top to bottom to see how much penetration this procedure gets?

1. Like on a hidden tang knife. about 3/4, 7/8, etc. As deep as posible.

2. Probably not.

3. No, I can slice the material and use them for scales. The ones I tipically use are around 4x3x15 cm.

4. Of course, it was the first thing to test. And it was ALL saturated with resin. I will post a picture next week.

If you see the last picture, you can see a 45 degrees cut on the end of the piece. As you can see by the polishing, it's all resinated.



What resin do you use?

Polyester resin, diluted to be liquified enough (10% SM).



how long does it usually take before you turn of the pump? and how do you stop the resin from being to thick? do you thin with acetone maybe?

It takes me 6 minutes to start seeing the resing getting thicker on the hose end. To liquify it I use Styrene monomer up to a 10% of the resin.



What is the average time period for a piece to get completely saturated?

About 6 minutes for the size I posted (4x3x15 cm.)

This is for a room temperature of about 20C, but it also depends on teh manufacturer, how old the resin is, the drying time, the ammount of styrene monomer that it has, the % of dye (if any), etc.



how deep does the resin penetrate? can you contour the wood or make finger grooves?

The entire piece gets resinated, so you can do whatever you'd like with the finished piece.



How long does it take before the resin starts to harden? Have you tried this with any other type of resin or epoxy?

6 minutes. I can't use epoxy resin as it doesn't get liquid enough.


Regards :)



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