We pick up where we left off last time in Part 1 with the procedure for making brazing paste.
5. Procedure for making brazing paste:
- 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.
- Begin with roughly equal volumes of BFM and gel binder. You can easily modify the amounts used, based on your experience. You can then modify batches to make them thicker (higher viscosity) or thinner (lower viscosity) by adding more (or less) gel binder to the mix.
- 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.
- Add the ingredients to the mixing jar:
- Add about half of the gel binder to the bottom of the mixing jar, then 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 is encased with gel binder above and below the powder.
- Tightly seal the container. Usually, a screw-on cap is preferred for best seal.
- Place tightly capped container into clamping arm of the paint shaker, and tightly clamp the jar onto the center of the clamp-arm surfaces.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.
- Blend the mixture for approximately 10 minutes. You can make the time shorter or longer based on your experience.
- After the paste container has been removed from the shaker, test the viscosity for your needs, and modify it as necessary.
- 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). NOTE: Hand-mixing may be OK for small quantities of BFM paste that will be used quickly, but it is not recommended for larger quantities that will be stored for longer periods of time.
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.