Quote Originally Posted by Troggie View Post
There is a thread in the Workshop area of a Tool that Harbor Freight carries that may work. Spot Sanding Prep Pen

The other thing is to protect your blade you can put a light coating of oil on the blade to help prevent this in the future. I use gun oil for mine but they are all vintage blades with no etchings or anything on them so not sure if it would affect that.

I know you said you dried the blade but how did you store it if you laid it flat than any moisture in the air or residual on the blade would have just sat there.
That spot pen looks a cool tool if its not overly abrasive.
We've had a solid week of rain here. I've taken to covering my open blades with tissue paper while drying overnite to prevent condensation settling on them.