Hi Karla,
I’m so sorry – I have just seen your comment here all these months later – it seems we weren’t receiving forum notifications properly back in August/September last year.
Not sure if you’ve had a go at producing some cardboard spawn and found your way in the meantime, but here’s the answer to your questions in case:
1) it is cardboard, the type you get from cardboard boxes (apologies I think card may have two different meanings outside the UK)
2) to pasteurise the cardboard, you just use hot water, poured onto the card and left for 5 minutes, before carefully draining it and squeezing out any excess water.
3) after mixing them together, leave them in the warm for a couple of weeks until fully colonised
Hope this helps – it’s a great way of producing a bit of your own spawn from mushrooms you’ve just grown!
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