I just picked up some vintage Hornsea pottery and want to know if its microwave safe! Its from the Heirloom collection, which was manufactured in the 60/70s. I don’t own a dishwasher, I want to know about the MICROWAVE. Thanks. Remember that back in the 60s domestic dishwashers were not very common. Nowadays dishwashers work at much higher temperatures and the cleaning agents that we use are much stronger. If you put Heirloom in the dishwasher, the glazing will almost certainly craze quite quickly, so I would not recommend it.