Everything @AliOop said.You are talking about dried-up lye solution on the rim; that is a different issue than precipitation, and it doesn't affect the strength of the remaining solution. To prevent the buildup, wipe the pouring edge completely dry after each pour, and before you reattach the lid.
Precipitation happens when the NaOH "un-dissolves" from the water and falls to the bottom of the container, usually due to a temperature drop to 65F or below. The undissolved or precipitated NaOH often solidifies into ice-like chunks or crystals at the bottom. That IS a problem and DOES affect the concentration of the remaining liquid.
Last edited: