Boric acid fluxes...

[DrB]

I'm in the mood to experiment with alternative fluxes. In the past I've used materials from coffee grounds, to grease, to a bead of bullet lube.

I mostly cast pistol bullets using a bottom pour pot, but am starting to cast more for rifles... Working with some new molds, many of the bullets I produced have what appear to be gray inclusions. When using graphite tumbled hard lead shot for arsenic content, I've also noticed what I suspect are graphite inclusions originating from the graphitec surface of the shot, even after fluxing (since graphite should easily float to the top, if it is graphite, there must be some serious wetting holding it in the lead). I'm suspecting I'm not sufficiently fluxing my lead, or the flux I'm using is not doing a good enough job. While my pistol bullets have always shot more accurately than I have, I'd like a better standard for rifle bullets -- since I can shoot them much more accurately than pistol bullets and will be pushing them harder, I am more concerned for their uniform quality.

Also, most of my improvised fluxing materials are smoky as heck (burning coffee grounds also stink).

Since I've read that boric acid based fluxes are smokeless and form a layer of glass on top of a pot of lead, and I've got plenty laying around, I've thought of playing with boric acid based fluxes.

Any suggestions for diagnosing my inclusions, improving my technique, formulating a boric acid containing flux, cautions, or hazards for same?

Thanks in advance for your contributions.

[lurch]

Boric acid fluxes work BUT...

They leave a residue in the pot that is very hygroscopic and will cause rusting if it is not removed (at least in humid areas). The residue is also very tenacious in its hold on the pot walls and cleaning it out is a real chore. The only way I was able to really get the stuff out of my pot was to use a wire cup brush on a drill, which produced copious amounts of dust in the air. A dust mask is strongly recommended for this task as the dust can contain lead oxide which is not exactly healthy to breathe. Outdoors is definitely preferred as well.

It's been a long time since I used any but I do remember that I got better results reducing the oxides on the top of the melt back to useable metal with plain paraffin. Yes, it smokes but the fumes can be lit and that reduces the smoke considerably. I just open the garage door when I'm fluxing and live with the stink.

There are those that do like and use the boric acid flux. I'm not one of them.

[dragonrider]

Have you tried straight sawdust, any species. Smokey yes but light it on fire and it won't be. It WILL flux your lead, it WILL keep your pot clean. It WILL clean up a dirty pot. I WILL never use anything else. Read stickies and do a search and you will find many post on the subject.

[cbrick]

Marvacrap is the same thing, boric acid.

About 10 years ago was one of the happiest days of my life. It was the day I discovered sawdust as flux and tossed the Marvacrap in the trash.

Here is something to read on flux. Chapter 4 will answer more fluxing questions than you knew you had.

From Ingot To Target (http://www.lasc.us/Fryxell_Book_textonly2.pdf)

The entire book is a great read but chapter 4 answers your questions on flux.

Rick

[geargnasher]

Before you get "experiement happy" with that borate krap, read this: http://www.lasc.us/FryxellFluxing.htm

Gear

[geargnasher]

BAH! Rick, where have you been? Beat me by a minute!

Marvacrap, what an apt name.

Gear

[cbrick]

And I had to type really fast to get it in on time too. :mrgreen:

Rick

[geargnasher]

I gotta get those links on speed dial....[smilie=l:

Gear

[DrB]

I gotta get those links on speed dial....[smilie=l:

Gear

Wilco, re reading homework.

Thanks cbrick, gear, lurch, and dr for the the references. Thanks particularly to rick for the chapter four suggestion. I've seen it referenced before. Guess its time to read it.

Yeah, I've plumbed the lasc site pretty thoroughly. Just figured grounds were close to sawdust and I wasn't impressed by the graphitic inclusions post fluxing. My first principle for anything has been that if what you are doing isn't working, stop doing it and try something different. Boric acid would be very different. That said, there's little to be learned from repeating others failures...

I was using a wax based lube for those rifle bullets.

Next stop chapter 4 and hickory sawdust.

[geargnasher]

Fluxing with dry coffee grounds make your boolits go faster. :shock:

Gear

[DrB]

Fluxing with dry coffee grounds make your boolits go faster. :shock:

Gear

So you've tried it too! :)

[DrB]

Fluxing with dry coffee grounds make your boolits go faster. :shock:

Gear

I started out using decaf grounds, then figured out I could save a grain of bullseye in my plinking loads using regular.

[geargnasher]

Actually, I did. Thought it might smell better than sawdust. It did for about thirty seconds and then it started to smell like a tire fire. I'll stick with aromatic hardwoods or pine knots and stirring with a maple stick.

Gear

[DrB]

Yep. It stinks just like a coffee roasting facility (which always seemed odd to me given roast coffee smells good). ' course, I wear a hepa mask + run an exhaust fan when I'm doing heavy fluxing, so it doesn't bother me much till I smell it on my clothes later.

Any reason for maple, particularly?

[madsenshooter]

I use either citric acid or paraffin. Though some will say otherwise, I think the boric acid stuff makes its own inclusions, but that was when I first started casting and I was stirring the stuff in. Someone here said was the way to do it, the way he does it, I bet he makes interesting boolits. The citric acid will smoke, and it is an acrid smoke, not suggested if you have asthma. It releases hydrogen so you can light it to stop the smoke. The smell after that is somewhat like baked goods. The citric acid is very good at reducing oxides as it has 3 hydrogen protons to donate, the paraffin works best for reducing surface tension I believe. I forgot to mention, it's anhydrous citric acid, as used in animal feeds, not the stuff you get for canning, which contains silicon dioxide, which I'm sure will make occlusions.

[geargnasher]

Yep. It stinks just like a coffee roasting facility (which always seemed odd to me given roast coffee smells good). ' course, I wear a hepa mask + run an exhaust fan when I'm doing heavy fluxing, so it doesn't bother me much till I smell it on my clothes later.

Any reason for maple, particularly?

I have a lot of straight-line trimmings of various hardwoods from a friend's cabinet shop, little strips about 7/8x3/4" and eight or ten feet long. The maple makes great stir sticks because it doesn't absorb much moisture, it chars slowly, and it stinks less than most other woods I've tried. For sawdust anything will work.

Gear

[Longwood]

A $5.00 40 pound bag of pellet stove pellets will make about three bags of sawdust if you wet it and let it dry in the sun. I have been using it for a couple of months along with some paraffin and get the cleanest melt and prettiest bullets that I have ever seen since I started casting in about 1974.

[DrB]

Lw, thanks for the tip!

[DrB]

Madsenshooter, thanks for the citric acid tip. I've got two feedmills close by, so I may be able to try that out.

As someone here has suggested, I do get experiment happy. :)

Btw what application rate per twenty pound pot would you suggest?

[cbrick]

Yeah, I've plumbed the lasc site pretty thoroughly.

So what did you think of that lasc web site DrB?

Rick

[madsenshooter]

Madsenshooter, thanks for the citric acid tip. I've got two feedmills close by, so I may be able to try that out.

As someone here has suggested, I do get experiment happy. :)

Btw what application rate per twenty pound pot would you suggest?

1/2 teaspoon in a 10lb pot makes a pretty good sized fire. Depending on the temp of your melt, it'll eventually burn down to a powdery yellow and white ash. Don't forget to have your lighter at hand when you put it in, the smoke before it is lit is quite acrid, and will burn your eyes and throat. Don't ask me how I know.

[DrB]

I liked the lasc site, rick.

They covered alloy fundamentals well, as well as points regarding what scrap lead NOT to use and why. As an overeducated engineer I appreciated their lube pumping discussion as being much better than what seemed to me oversimplified or poorly thought out discussions (i'd still be interested to see a rom calculation of the respective stagnation pressures as a function of caliber, rpm, average acceleration, etc. I expect some plots would show that different mechanisms are important at different times). The page referenced above re fluxing is by one of the same authors (fryxell) as the cast bullet book... It is technical and seems well written. Didn't they also do a bullet hardness testing comparison of various testing products? I thought that was outstanding! I'd like to see more collaborative projects like that and of that quality.

Overall, I though the lasc site was good. I read most of what they had up a couple of years ago. Like many things, I'd like to see more plots/data, but that's because I am who I am, and I recognize that's not who the general audience is.

That's my two cents, Rick. :)

[cbrick]

Good writeup DrB, not that I was fishing for compliments or anything. [smilie=1:

Rick

[geargnasher]

Glen Fryxell has, as I understand it, earned a doctorate in chemistry, which explains a lot about why he can write, present ideas clearly, and why he has such a good understanding of the chemistry of boolit metals.

Gear