Compare the colour of spores mounted in Melzer's Reagent to the colour of spores mounted in water. The reaction should be immediate, but if in doubt about any colour change, leave for 20 minutes.

The reaction to Melzer's Reagent may be strengthened following pretreatment in alkaline solutions such as weak KOH or concentrated NH₄OH. Place lamellae in the alkaline solution, then remove and rinse in water prior to mounting in Melzer's Reagent.

Note: this character is only used if the Spore colour (microscope) state is either hyaline or pale, as the reaction is less obvious for darker pigmented spores.

Choose this state if: spores become reddish brown (or occasionally purplish brown), but not bluish, when mounted in Melzer's Reagent. This reaction is also called pseudoamyloid. In a fresh collection, the dextrinoid reaction may be more pronounced in older, discharged spores, which can be found on the surface of the pileus. In dried material, the dextrinoid reaction may be less pronounced with age of the collection.

Compare the colour in water in case the spore colour is naturally reddish brown.