I'm not familiar with the word, but the comparative form of multi-syllabic adjectives is formed by adding the word "more" in front of it. The superlative form of multi-syllabic adjectives is formed by adding the word "most" in front of it.
comparative : purer superlative : purest
Comparative: older Superlative: oldest
Dative; Early Comparative; Earlier Superlative; Earliest
The comparative and superlativeforms of grand are: Comparative: grander Superlative: grandest
comparative - merrier superlative - merriest
comparative = sadder superlative = saddest
Comparative: shallower Superlative: shallowest
The comparative is "stricter" and the superlative is "strictest".
The comparative is greater and the superlative is greatest.
Comparative is more and superlative is most.
comparative straighter and the superlative the straightest
Comparative: thinner Superlative: thinnest