By Dan Kay
It is erroneously believed by many that brazing filler metal (BFM) pastes need to be refrigerated prior to use, or for long-term storage. This has led to misunderstandings and difficulties in the handling and use of BFM pastes in many shops, and to incorrect, misleading product labels.
Having been involved in the manufacture and testing of brazing pastes for many years, I will categorically state that there is nothing inherent in the chemistry of brazing pastes that requires their refrigeration! Some industry specs (and some cartridge labels) still state: “This paste must be refrigerated prior to use”. This very misleading statement has caused some people to believe that the paste must be cold when used in order to perform properly. This is completely wrong! Cold brazing-paste is much stiffer and harder to extrude (which can also be dangerous), and serves no useful purpose.
Bear in mind that a refrigerator can actually de-humidify objects placed therein (you know this from what happens to vegetables that are stored unprotected in refrigerators). The water content of the gel-binders in brazing pastes can actually be slowly removed by steady refrigeration, even though the paste is in plastic cartridges, since the cartridges aren’t actually as well sealed and “water-tight” as thought.
Many years ago, brazing was done in hot brazing shops (since there were very few cold-wall vacuum furnaces back then), and it was felt that refrigerating the brazing paste was the best way to protect it from the potentially damaging shop heat (which can cause paste to dry out or the gel-binders to break-down). But over the years this has changed significantly, and such refrigeration-suggestions really do not carry much meaning anymore. Please note that there is absolutely nothing about refrigeration that has any benefit to the paste’s ability to perform. It was merely an old-time suggestion made to keep the pastes from breaking down in high heat environments.
All that is required for BFM paste storage today is that it be protected from any dirty/oily shop atmosphere and from excessive heat. Thus, by keeping the BFM paste cartridges in a storage cabinet, at ambient temperature, in the room where the BFM is applied to the parts, or in an insulated cabinet (such as the yellow safety cabinets in use today) out on the shop floor (if the BFM paste is applied to the parts out in the shop), you will achieve all the desired level of protection to the paste that is needed.
Therefore, it is NOT necessary to ever refrigerate the paste! Specs and labels requiring refrigeration should be changed!
NOTE: If you want to use a refrigerator to store BFM paste, that’s fine. Just unplug it! Then it makes a fine storage cabinet!
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