When mixing a two-part sealant, the end goal is a thoroughly mixed aviation sealant that cures and adheres to the surface properly. What do we mean by “thoroughly mixed?” The base and catalyst should be mixed until the mixture has the look of one consistent color. Sounds easy right? Not exactly.
Because if the two parts aren't completely mixed, then the sealant just isn't able to do its job. A couple of different scenarios can happen:
1) The sealant may not cure and achieve the hardness required.
2) The sealant may not adhere properly to the its intended surface.
When you are working on a tight schedule and need to get a plane out the door, it can be frustrating to go through the mixing and application process only to find that it's just not working.
We've gotten many phone calls over the years from customers who experience this exact situation. We have even visited customers' facilities to view their sealant mixing process. This is because we want to better understand why the sealant is passing our internal lab quality checks but not performing in the customer's real-world application. Customer service is our top priority.
Here are two simple but key dos and don’ts for applying two-part aviation sealants. We can't tell you how many times these tips have come in handy over the years!
Do: Be careful when mixing a kit with a mechanical mixer, particularly a hand drill. If you choose to use a drill, be sure to only use low speeds as recommended by the manufacturer. If mixed at high speeds, internal heat can be generated and reduce the amount of time you have to apply the sealant. Best practice, per the manufacturers, is to mix by hand or use an approved manufactured mixer.
Don't: Forget the rule of thirds when mixing a semkit or techkit hand. To ensure even distribution, insert one-third of the catalyst into one-third of the base. You’ll do this step a total of three times, inserting catalyst at the bottom, mid-point, and top of the cartridge of base.
To mix the catalyst and base evenly, simultaneously twist the mixing rod clockwise while pumping it repeatedly from the top to the bottom of the cartridge until you have an even distribution.
Even distribution can be gauged by the uniformity of the color.
We hope this helps. Feel free to reach out for clarification or other questions.