Try this ... we did it several times and it has amazing effects ...

put a small can of water on your stove and have it boiling. Then dip two common wooden clothpins into it for some seconds ... then apply them to your slave nipples ... the burning sensation will last for a long time and she will buck and jump ... I loved it very much to penetrate her before applying the pins in order to enjoy her cunt's contractions ...

Be careful to the time you keep the pins in the boiling water, the longer you keep them, the longer the effect lasts.... and remember also that the effect is cummulative. that's to say that even if you don't become to severe, the burning effect of all successive applications will cumulate and may bring to the same consequences of 1 long application.

One time we enjoyed it quite extensively, with very long lasting pain and caroline got both nipples burned ... though they came back to normality in a couple of weeks. So I advise to increase the dipping time gradually and wait to see the reactions of the skin.