Ko te Hydroxypropyl Methylcellulose (HPMC) he tāpiringa matua i roto i ngā piri taera, he pānga nui ki tā rātou mahi, inā koa i roto i te wā tuwhera. Ko te wā tuwhera e pā ana ki te wā e mau tonu ai te piri taera me te kaha ki te hono pai i ngā taera i muri i te paninga. He mea nui te pānga o te HPMC cellulose ether ki te wā tuwhera o te piri taera kia angitu ai te tāutanga taera, inā koa i roto i ngā taiao uaua.