This is Part 2 of the article Shelf-Life and Expiration-Dates for Brazing Paste
Brazing paste is not difficult to make yourself. All you need is some brazing filler metal powder, a gel-binder, and a paint-shaker. Sound easy enough? Let’s see…
First, procure the desired brazing filler metal (BFM) in powder form from one of the BFM manufacturers. I show a listing of such manufacturers on my website, and each company’s name is a “hotlink” to that company’s webpage.
Secondly, procure some gel-binder from one of those BFM suppliers, too. Some manufacturers do sell gel-binders as separate items, whereas other manufacturers will only offer their gel-binder systems as part of a pre-blended system with the BFM. Those manufacturers who do offer gel-binders will usually sell them in a variety of container sizes, ranging from about a quart up to gallon-size containers.
Thirdly, locate a good paint-shaker for blending the BFM and the gel-binder. Such paint-shakers are usually found in company labs or maintenance areas, or they can be found at your local community’s paint store. Obviously, they can be purchased on-line as well.
Fourthly, procure the plastic cartridges into which you intend to load the brazing paste that you make. These dispensing cartridges are usually packaged in boxes that also contain end caps and pistons for the cartridges.
Lastly, procure empty containers (plastic bottles are preferred) in which you will mix the materials to make your brazing paste, and from which you will pour the paste into the dispensing cartridges.
Procedure for making brazing paste:
1. Determine how much paste you will want to make at any one time. I would suggest making only enough to last a maximum of about 30-days, so as to avoid having the binder-systems break down by being on the shelf too long.
2. Begin with roughly equal volumes of BFM and gel-binder to use. You can easily modify the amounts used, based on your experience. You can easily then modify batches to make them thicker (higher viscosity) or thinner (lower viscosity) by adding more, or less, gel-binder to the mix.
3. Please note that the total volume of the BFM and the gel-binder that you will be mixing together should be approximately two-thirds to three-quarters (maximum) of the total empty volume of the mixing jar you are using. You must leave an air-space at the top of the jar so that the mixture can move (“slosh”) back and forth adequately for good mixing/blending to take place.
4. Add the ingredients to the mixing jar:
- Add about half of the gel-binder to the bottom of the mixing jar.
- Pour in all of the BFM powder.
- Pour the remaining half of the gel-binder on top of the BFM powder. Thus, the BFM powder in encased with gel-binder above and below the powder.
- Tightly seal the container (usually a screw-on cap is preferred for best seal).
5. Place the tightly-capped container into the clamping arm of the paint-shaker, and tightly clamp the jar onto the center of the clamp-arm surfaces.
NOTE: It is often desirable to use rubberized surfaces in the shaker’s clamping/shaking arm, so that the BFM-paste container cannot fly out of the clamping arms during the mixing process.
6. Blend the mixture for approximately ten (10) minutes (you can make the time shorter or longer based on your experience).
7. After the paste-container has been removed from the shaker, test the viscosity for your needs, and modify it as needed.
8. Load the dispensing cartridges with the paste you just made.
This paint-shaker process can create very creamy brazing paste that will remain creamy and stable (no separation) for many weeks! It requires very little expenditure of energy on your part, since the paint-shaker does all the work, and the stability of the paste far exceeds anything achievable by hand-mixing (whether or not you use electric drills with paint-mixer tools attached, or try to vigorously stir it by hand, etc.).
A key advantage to this process is that you are keeping the BFM powder and the gel-binder in separate containers until they are needed. In that way, there are no shelf-life concerns because the BFM powder and the gel-binders don’t have any shelf-life limitations at all when kept in separate containers.
Have some fun by trying this out for yourself!
Next Month: In next month’s article, we’ll consider brazing stop-offs, and how they are correctly and incorrectly used in many brazing shops today!
Dan Kay – Tel: (860) 651-5595 – Dan Kay operates his own brazing consulting/training company, and has been involved full-time in brazing for 40-years. Dan regularly consults in areas of vacuum and atmosphere brazing, as well as in torch (flame) and induction brazing. His brazing seminars, held a number of times each year help people learn how to apply the fundamentals of brazing to improve their productivity and lower their costs. Dan can be reached via e-mail at [email protected], and his website can be visited at: http://www.kaybrazing.com/
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