硫化 りゅうか変色 へんしょくじゃないです
ryūkahenshokujanaidesu

Noun
Desu Copula
Negation Auxiliary

The polite negative form of 硫化変色

1. It's not discoloration due to sulfurization.; It's not a change in color due to sulfur.

Negative
Polite
Casual Register