Wave Solder of White Tin Emmersion Finish

Would anyone out there happen to have some experience with wave soldering of white emmersion finish pcb's? Recently, we have done some prototype boards in white tin. The reflow solder joints look very good, but the wave solder joints look grainy. Is a grainy appearance to be expected with white tin finish pcb'? We use a very mile no clean wave flux. The solder pot temp is 495 F and top side temp we shoot for is 230 F.

Thanks, Pat Pepper

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