Can liquid flux be evaporated to make paste? - Page 1
Forum section: electronics / beginners

author: pcm81
author_rank: Regular Contributor
timestamp: August 16, 2025, 03:22:47 am
content: With heating and stirring in a glass beaker and magnetic stirring bar, can i thicken kester 2331-ZX and/or Kester 186 to turn them into paste/gel for manual pcb rework? I got 1 gal jars of each but would like some paste like Amtech NC-559.I know kester makes a thinner, but does kesster make a thickener for these fluxes? Haven't seen thickener on their site; so that i why i though about boiling off some solvent.Thanks ahead

author: John Coloccia
author_rank: Super Contributor
timestamp: August 16, 2025, 05:02:39 am
content: Quote from: pcm81 on August 16, 2025, 03:22:47 amAll you're going to do is evaporate the solvent it's dissolved in. It's like you can't mix chocolate powder into water, and then evaporate it to make fudge.In the future, for 186, I buy the pens. And the pens SUCK, but I pull off the ends and pour them into my little vials with brushes in them. Because for real, almost none of us need a GALLON of flux.

author: pcm81
author_rank: Regular Contributor
timestamp: August 16, 2025, 05:12:47 am
content: I realize that i will evaporate solvent. What i was hoping is that the resin in 186 or organic acid in 2391 would produce thicker substance with higher solids concentration. but i do not know if some other, more required, components would evaporate off as well.

author: pcm81
author_rank: Regular Contributor
timestamp: August 16, 2025, 05:15:01 am
content: Quote from: John Coloccia on August 16, 2025, 05:02:39 amI am about 0.1Galon through the 1 gallon jug i bought in 2010. I'll report back in another 135 years.

author: David Hess
author_rank: Super Contributor
timestamp: August 16, 2025, 06:04:48 am
content: It will probably crystalize. Solder pastes have things like glycerine added to prevent this. Check some MSDSes.

author: tooki
author_rank: Super Contributor
timestamp: August 16, 2025, 08:37:40 am
content: Quote from: pcm81 on August 16, 2025, 03:22:47 amNo, it won’t work, for the simple reason that liquid flux isn’t fluxpastedissolved in solvent.Think of it like this: does boiling down Kool-Aid make Jello? No. Because the gelling is provided by a different substance.Liquid flux is fluxing agent dissolved in liquid solvent.Paste flux is fluxing agent dissolved (or dispersed) in a paste vehicle (that can be vaseline, or various other things)The fluxing agent itself is whatever combination of rosin, resin, acid, and/or activators used in a given flux.Evaporating the solvent from liquid flux won’t suddenly add a paste vehicle to the flux.You should just buy a tacky flux. Kester makes a bunch, but good luck finding any way to buy them in smaller quantities than a crate.So buy Stirri (the new name for Amtech flux; anything sold as Amtech now is fake, as I understand it), or Chip-Quik, or MG Chemicals, or Caig, or SRA, etc. from a REPUTABLE distributor (=not Amazon, not AliExpress, not eBay, not temu, etc).

author: bte
author_rank: Regular Contributor
timestamp: August 17, 2025, 05:26:32 pm
content: Quote from: tooki on August 16, 2025, 08:37:40 amNorthridgeFix still sells authentic Amtec flux. From what I understand, Inventec still retains the rights to the Amtech name and some of the old formulations so the "Amtech" name itself doesn't indicate fakeness (assuming, of course, that the purchase is done through a reputable dealer).Here are some Reddit threads I could find about the topic. I have no means to verify the accuracy of the claims, but they sound plausible.https://www.reddit.com/r/soldering/comments/1dd51t1/amtech_and_stirri_confusion/https://www.reddit.com/r/soldering/comments/1g5ss2r/if_you_were_in_a_meeting_with_amtech_what_would/https://www.reddit.com/r/consolerepair/comments/196rqsz/best_place_to_source_legit_amtech_flux_from_online/https://www.reddit.com/r/soldering/comments/1jneowe/anyone_tested_new_soldering_flux_from_stirri_v4tf/https://www.reddit.com/r/soldering/comments/18boa1j/amtech_559_asm/https://www.reddit.com/r/soldering/comments/16jh4iu/comment/kjbjy6f/

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: August 17, 2025, 05:34:27 pm
content: I recently bought and used some gel like flux from Micro Center, I think it works fine and sticks to the parts well. Maybe someone else had different opinion but for my purposes, it works well>https://www.microcenter.com/product/657387/sra-soldering-products-no-clean-tacky-flux-2cc-squeeze-tubes-6-pack

author: pcm81
author_rank: Regular Contributor
timestamp: August 17, 2025, 10:04:10 pm
content: So, here are my updated thoughts on the matter:1. liquid flux evaporation: I evaporated some Kester 2331 to about 10-20 percent by volume. The resulting flux leaves heavy residue, as expected since 2331 requires cleaning and now i have about 5x concentration of solids. Will try mixing with petroleum gel to get it into a paste form. Not supper concerned about residue from petroleum gel since this flux requires cleaning anyways.2. I totally dig the positive reviews of Amtech 559 V2, but with all the 559 ASM swicharoo i am very hesitant to buy it. The whole idea of using no clean flux is that you can trust it to not need cleaning. But if i am taking a chance that i get the ASM version instead, then might as well go for aggressive flux and clean appropriately afterwards.3. Will try to evaporate some Kester 186 and see how that goes. might try to mix it with petroleum jelly if i can convince myself that petroleum jelly and its burn products are harmless. advantage of 186 vs 2331 is probably with stranded wires, since the flux that gets sucked in under insulation by capillary action is there to stay...

author: tooki
author_rank: Super Contributor
timestamp: August 17, 2025, 10:22:57 pm
content: Quote from: pcm81 on August 17, 2025, 10:04:10 pmWell let me pop that bubble right away: “no-clean” fluxes are only safe to leave on if they have beencompletelyheated to their neutralization temperature.This is not guaranteed to happen when hand soldering, and in fact is pretty much guaranteed to not happen.In other words: no-clean liquid or paste flux is only safe to leave on when used for reflow soldering in a reflow oven (or vapor phase machine). So it really is “no-clean” for mass production with carefully-dosed solder paste, which is what it is designed for.Even when you reflow a board at home, if there is too much flux residue, it can be safe to leave on, but make inspection difficult, requiring you to remove it anyway.When you hand-solder, whether with hot air or a soldering iron, some of the flux will flow away, onto cooler parts of the board, and never get heated hot enough to neutralize. (The only exception is the flux core in solder wire.) So when you use “no-clean” flux for hand soldering, you must clean flux residues.So at the end of the day, for home use (or other similar prototype usage), you can pretty much forget about the “no clean” aspect. Traditional rosin fluxes are often easier to remove than no-clean fluxes, so they can actually belesswork than “no-clean” fluxes.If you have an ultrasonic cleaner, one option is ChipQuik’s water-washable no-clean flux products (4300 series). They are fundamentally safe, but wash off on hot water. They clean off really, really well in just a few minutes in an ultrasonic bath of hot water.

author: pcm81
author_rank: Regular Contributor
timestamp: August 17, 2025, 11:04:57 pm
content: Quote from: tooki on August 17, 2025, 10:22:57 pmYeah, i am pretty sure you are spot on with this one; but then it means my 14 year old jar of kester 2331-ZX is as good as it gets for home use; since i have to clean it no matter what. But, but i wanna i wanna new better stuffs...

author: pcm81
author_rank: Regular Contributor
timestamp: August 17, 2025, 11:44:29 pm
content: Can someone help me locate the correct dispenser for the 170g cartridge here:https://stirri.com/products/stirri-v3-tf?variant=46674149441853Their dispenser page is coming up blank for me.

author: tooki
author_rank: Super Contributor
timestamp: August 18, 2025, 12:11:27 am
content: Quote from: pcm81 on August 17, 2025, 11:04:57 pmAnd meanwhile, many of us pine for the traditional products that are no longer made (like Kester 44 paste and 1544 liquid)…