I only made one paper bear as part of my MA course work but was asked if it was for sale. I would never sell the original as I'd not considered how archival the materials would be. I sourced  a few more copies of the book but as they were all decades old, the paper was already deteriorating. .

The pH tester pen tests for the acid in paper.. the pale yellow lines at the top of the pages shows the acid is high. After searching reviews I found several people recommending Make it Acid Free and bought some on Amazon for about £30. 

I sprayed boths sides of each page and retested with the pen. The lines stayed blue indicating that the acid was neutralised. Perfect! ...Or so I thought, but next morning the blue lines were yellow again. I wasn't sure if the spray was faulty so retreated the pages several times but with the same results.

 The Amazon seller agreed to refund my money if I returned the can. When I looked up postage on Royal Mail it turns out it is illegal to send aerosols through the post so it should never have been sent in the first place. This  seems obvious when you think of the hazard it could cause.  Eventually I did get my refund without having to return the can but I did feel bad that the seller was out of pocket.