I have always used sawdust or wax but I have some leftover borax and was interested if anyone has seen a benefit from using it instead of more popular alternatives.

Don’t.

Easy answer this !

Well I guess I will not give it a try then.

Like JD MT, I have used sawdust to great success.
Thin layer of ground charcoal briquettes seem to work nicely also.
I think it works as an insulator to keep the temp more even and reduces the tin oxidation also.
Unlike most folks I cut my sprues right back into the pot.
Seems everybody has their "special way.
For normal fluxing it is plain old candle wax.

Doesn't borax cause rusting of the pot in humid climes?

borax,

sometimes you just have to say NO to the good idea fairy.

As good a flux as you can use... Like the old shooters used & has been forgotten. Unsalted lard or rendered fat from your last hunt. Inexpensive unsalted lard from your local grocer is as good a flux as you can buy.....

Never heard of anyone using borax...

This guy is using 20 Mule Team Borax to flux his melt,,,,,,,,,,,, I think I'll pass.

https://www.youtube.com/watch?v=74GXkb9BvYc

Off topic, but interesting health benefits about borax. ( boron).

"The boron conspiracy"

(About how Australian Parliament squashed a threat to big pharmacy about borax/boron's anti-inflammatory benefits for arthritis)

https://nexusnewsfeed.com/article/c...-how-the-arthritis-cure-has-been-stopped


-----------------------------------
"Nothing boring about boron"

(Interesting article about several health benefits of boron / borax)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4712861/

============================================

"20 Mule Team Borax" is sodium tetraborate.