Flux is a wonderful goo that makes soldering faster and easier. In previous videos we compared different types of commercial flux (Flux off 1, Flux off 2), but did you know it’s possible to make a simple and effective flux at home? We’ll get you started, and don’t miss the giveaway at the end of the video.
Arhi shared his method of dissolving rosin into a solvent. Rosin is an inexpensive processed tree sap, used on violin bows, art, etc. It’s also the primary ingredient in many fluxes. Followup comments revealed an expired patent with a simple flux recipe:
- Isopropyl alcohol (60-70% by weight)
- Water white rosin (30-40% by weight)
- Glycerin (2-3% by weight)
- Cationic flurocarbon surfectant (0.01-1% by weight)
- Liquid flux is produced using a 20-65% concentration of rosin; at concentrations of 65-80% of rosin, a paste flux is produced
Ignoring the Cationic flurocarbon surfectant, everything is readily available.
A reader donated a kilo of craft rosin, but you can find it a craft and music stores. We powdered it in an envelope with a hammer to it would dissolve faster. The nearest drug store had both isopropyl alcohol (96%) and glycerin. One thing the video doesn’t mention is the alcohol strength. It should be 96%, not lower strength 70% rubbing alcohol.
We mixed test batches in 3 proportions:
- Thin – 60g alcohol, 40g rosin. Same viscosity as alcohol alone
- Medium – 35g alcohol, 65g rosin. Starting to thicken a bit, like cooking oil
- Paste – 20g alcohol 80g rosin. Quite thick
Glycerin is optional, but is said to prevent the rosin from burning and discoloration under high heat. We added just a few drops, but skip it without worry.
Is it any good? Actually, it beats a lot of the commercial flux off contenders. It barely smokes, it doesn’t smell bad, and it didn’t discolor. The residue can be left on the board, or wasted off with more alcohol or acetone.
If you’re ready to try it yourself, we’ve giving away four 100g bags of flux. Just leave a comment below and we’ll pick the recipients tomorrow. Bonus points for interesting formulation proposals.
A huge thanks to the reader who sent the rosin and made the video and giveaway possible.