maybe everyone is misinterpreting what you mean by plastic/chem taste.
i have noticed that bubble tastes "harsher" than bho. and after smoking bho all day a rip of bubble certainly has a taste to it that i cant quite put my finger on (not the hash flavor)
my belief is that it is the screen releasing fumes, because i dont get this taste as bad when putting bubble on straight weed
need to try a ti screen myself
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