Dear Mr. Hart: I have read all your articles on Papercrete and find them very interesting. I have made my own Papercrete blocks and have had them tested for strength. I wish to make blocks to resell but unfortunately I have been told that there is a patent on the Papercrete blocks and that I would have to pay royalties to be able to sell them. The person that has the patent is Mr. Paul A. McKelvey from Redlands, California. I don't see how he could have a patent on Papercrete since it's been patented once, in 1928, and so many people have been using it since then. I would really like to know your thoughts on this subject.
After some digging around internet and a phone call, I was able to respond:
You are right that Mr. McKelvey should never have been issued a patent for that process, since it had already been patented. His patent is #5,785,419, issued on 7/28/98, and it was for a "lightweight building material and method of construction of cast-in-place structures" and the material comprises "cement, fly ash, cellulose fiber, and water."
Prior to his patent is #5,350,451, which was issued to Eric Patterson in Silver City, New Mexico (issued 9/27/94) for essentially the same material and process:
"A slurry composed of paper fibers, water, and cement that can then be used for a variety of construction applications is prepared. After draining the majority of the water, the slurry may be molded into blocks, sheets, or any other desired shape to be used as a construction material, or it can be sprayed onto wire shapes to form custom structures. The slurry product can be used as a mortar in conjunction with building blocks that have been made from the slurry, and it can be used as a plaster when mixed with conventional cement and sand mortar. The slurry can also be poured into forms in the same manner as concrete to form blocks for construction applications."
The only material difference between the two patents is the addition of fly ash to the later patent, and that is a common additive to Portland cement and should have not been allowed as a significant difference.
In any case, I just talked to Eric Patterson by phone and he says that he is not enforcing the control of his patent and is offering his process and material for the general public to be used in any way they deem appropriate, without any expectation of remuneration or contracted commissions. So he suggests that you proceed with your project, and use his patent as the one under which you are operating. If you do not include fly ash in your formula, then Mr. McKelvey would have no recourse for making claims against you.