How to Chemically deinsulate the enamel of a copper wire ?

Thread Starter

q12x

Joined Sep 25, 2015
883
I have a lot of enameled pieces of copper wire to deinsulate. About 5mm long deinsulation at both wire ends. I dont want to deinsulate the entire wire, only its ends, ok?
The methods I used so far, for a very long time (tens of years), was to use a flame, or a knife to scratch the insulation. But because the wire I deal with is very thin, I can do 1 piece of wire at a time and it takes like 5 minutes until I finish both ends with the knife, which is very clean and precise job that I get from using it. But it takes some extra effort and time to do it and pain in my palm muscles if im doing too many pieces.
I want a CHEMICAL idea! A liquid that will melt or dissolve only the enamel of the wire, but not attack the copper, very important. I thought on acids, but they will eat the copper. Some sort of solvent specific for enamel.
I will try every idea you may have.
Thank you !
 

Thread Starter

q12x

Joined Sep 25, 2015
883
Try acetone.
In my language is called "diluant" and is a general purpose paint thinner (in eng). Is paint thinner stronger?or the same?or weaker? than acetone? Because I have paint thinner in house, but I dont have acetone. Or acetone is better solvent for enamel than paint thinner? Ill have to try them both in the end i guess... but until then... maybe I can escape with what I already have in house.
One method I have seen used is a solder pot, dip the end onto the pot and then quickly wipe off with a rag.
I didnt even know about the existence of a solder pot. Really interesting idea !
- More ideas please !
 

Thread Starter

q12x

Joined Sep 25, 2015
883
Yes, I googled for solder pot as well, and also I found on youtube as well.
Thank you about it, very novel idea for me.
But I want more ideas. Cheap will be best. Haha.
Also I dont have a wife, but I know what acetone means and for what is used. I simply dont have it in house.
Im testing now the "universal diluant". Hope it works. I believe acetone is weaker than diluant (paint thinner). I say it by the ear, by impression. But the composition of these substances is more important than their "power". Enamel is a category of paint, right? only it is a semitransparent paint. I guess. I really dont know much about enamel. I know a bit.
 

Andrew Leigh

Joined Sep 8, 2008
131
It depends on the enamel coating. If thin wire then there is a good chance it is a Polyurethane and will strip of in a solder pot. The polyurethanes were created for the electronics industry and referred to as "solderable enamel". If it is a Polyimide or a Polyimide with an Amide Imide top coat those are made to be chemically resistant and these were stripped with a mechanical stripper with rotating blades. I can remember what size the blades closed down to, probably 0.30mm diameter was the smallest. There were normally three heads available depending on the range you required.

Some chemist locally produced a chemical that would do the trick but the Health and Safety Data Sheet was something to behold.
 

Thread Starter

q12x

Joined Sep 25, 2015
883
Thanks all.
I did try a test with my "universal diluant" (paint thinner) and it didnt dilute the enamel. At least not fast enough. It might if I leave it over night, but... really I can scratch with my knife and finish the job faster. I like this ---mechanical--- way of deisolation of the enamel because is very clean and very precise. I am actually counting on the isolation of the copper wire to cross over each other multiple wires. So, heating, I know for sure, it will destroy or weaken the entire heat exposed surface.
I did 'simulate' your solder pot idea, with a molten blob of solder. It did nothing ! While holding the tip of the iron inside that blob to maintain it liquid. My best guess, it is not HOT enough, not at 400 dgr C or something, not critical enough temp to melt the isolation.
Then another try, because the power of the heat I guessed is lower than the melting point of the isolator, I put directly the tip of the iron on the end of the wire and hold it there until I could see a small solder sticking to the copper. But it takes like 30s to 1min to wait to burn that isolation, and is messy, it is creating a black thing, multiple causes for that black thing, not only the burned enamel, but also the resin I have on the piece of wood I hold the solder blob. And also I can see a discoloration of the enamel like 1cm away from the end of the wire. Which is not good in my book, I really like clean results.
I know, I know, I didnt do exactly what you suggested and I improvised. But I improvised it GOOD ! Haha.
You know what I wish? Still a mechanical thing, that is scratching very thinly and slow force, the enamel and leave the bare copper as I scratch it manually with my knife. MMMM....
Your solder pot must have a bigger melting point than the enamel can resist, if it is burning in a couple of seconds and not minutes like my tests I done here. Ugh.... Very tough thing !!!
 

Thread Starter

q12x

Joined Sep 25, 2015
883
Anyone, can you make a small movie for me? ... or even 2-3 pictures with before and after burned enamel and tell me how long you stick it in there and how HOT your solder pot was? If you have and use one. A movie will be great though.
Thanks !
 

MrSalts

Joined Apr 2, 2020
1,566
You will not have good luck, in general, with solvents. The "enamel" is generally polyurethane, polyamide (nylon), polyester (Mylar) or polyimide (Kapton) - sorted from cheap to expensive and low performance to high. These polymers are picked because they are pretty chemically inert.

If you do this often, look into wires that are meant to be soldered directly without stripping.

A simple method is to use very fine sandpaper. The finer the wire, the finer the sandpaper. Ive used 1000 grit for 42 gauge wire. Hold the wire on the bench snd move the sand paper. Roll the wire by moving your finger across the bench. You barely have to move to rotate 42-awg by 1/4 turn. You can also pinch the wire with a folded piece of sandpaper.
 

Thread Starter

q12x

Joined Sep 25, 2015
883
The biggest problem I face while deinsulate --mechanically-- (with my knife or sandpaper) is holding the wire into position, not to slip away. A considerable force I put to press it down and holding not to move, because if is moving, im losing it very quickly, it simply jumps into void, never to be found. So my hands get tired very quickly after 2 -3 wires like this. Try press for 3 minutes continuously and see how 'medicinal' is for your fingers and the muscles in your palm. I usually work with brakes, its a habit now, and is very effective. But it will be better to speed up this deinsulation problem.
If you have a solder pot, can you make me a very short movie, showing me how quickly and efficient the insulation is removed, please?
 

MrSalts

Joined Apr 2, 2020
1,566
Insulation on 42 gauge wire is so thin that 3 seconds is a better estimate of how long it should take to remove with very fine sandpaper - especially the pinching method.
 

dl324

Joined Mar 30, 2015
14,318
But it takes like 30s to 1min to wait to burn that isolation, and is messy
I tried using a soldering iron to remove the enamel on some wire that's 2-3 times the diameter of hair. It came off with half a dozen swipes. You can solder through the enamel if you're using it point to point wiring.

If you're okay with the wire getting tinned, the soldering iron with a blob of solder on the tip would work faster.

I tried acetone and it was taking longer than the soldering iron.

how HOT your solder pot was?
It just needs to be hot enough to melt the solder. The last time I used my solder pot, I didn't have an infrared laser thermometer, so I don't know what the actual temperature was.
 

Thread Starter

q12x

Joined Sep 25, 2015
883
I try what you say and show me with the iron tip and the drop of tin (also from the movie), but is not working on my wire.
1- maybe the insulation that I have is more resistant to heat than usual, maybe is a very good quality insulator, like @MrSalts said, they are many type of cheap and good quality. If it helps, mine have a darker red color , like the very old transformers from the 90's and 80's. The copper wire color in the movie, was almost transparent and yes I could see how FAST it melted away under the tip of the heat iron. Mine is like cement in there. I like it actually to be this resilient to heat. But now I need it not to be.
2- The iron heat is not that hot. After watching the video, I remembered that I have a knob on my heating iron station , and I turn it to maximum, repeated the experiment with the tin blob drop, I even put DIRECTLY the tip of the iron on the wire isolation, I wait like 30s to 1min and NOTHING ! I mean, I have to really scrub in all this time to actually reach the copper under the isolation and to see that starting wire tinning. I didn't measure the temperature of the tip of my iron though. I THINK is around 300 dgr Celsius. 350 maybe? At its maximum. And I usually run it at 70-80% from it's knob.
--
I also tried the sand paper method, and in my case, is creating a long transition from wire end with exposed copper towards the virgin insulator. I guess im not that used on doing it with sandpaper. I have very fine sandpaper of 250 grit. And it worked excellent but with a long transition compared with the 2-5 mm (precise removal with knife) that I require.
 
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k1ng 1337

Joined Sep 11, 2020
435
For a precision job you must know the purity of the copper and the formula of the solvent and wire coating and then balance the chemical reaction equation including ambient air or you risk side reactions and excess reagent. I learned the hard way with electroplating, namely prepping surfaces.
 
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