Render bags (Edgware HA8)

I’ve loads of bags left of render from when I done my shed. This render you have to scrap it afterwards to get the colour to come out. The picture of the shed is the colour. These bags have been stored in the shed for some time:

I have no idea how you do it. I do know it goes off - like I said I don’t know much about it. But I was told you can mix it with new stuff and it should be fine. But. Don’t know myself

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