DSF

Sounds like very slight staing if it is still nice and bright under the transfer paper. The teflon can still carry ink so might need a good clean. When I used to do t-shirts in the old days we used grease proof paper rather than teflon as it is disposable. Not wanting to ask a daft question but have you given the heat plate and the teflon a really good clean? I would have gone with medium pressure as well. Light can now and then leave the gassed ink escape more.

thanks Andrew. Yes, I'm using greasproof paper also and teflon on top of that. I'm going to buy new teflon sheet today and some better paper...