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Someone has an expired patent on a mixture that makes an oil painting medium. I will not use real names, but here are the ingredients of it

Painting oil  
+ Stone dust (gives medium a certain quality to it).

I want to make that patented medium thicker, by adding one ingredient, a third mineral dust.

So I would like to get patented this:

Painting oil  
+ Stone dust  
+ my mineral dust thickener 

If my medium behaves a little thicker than the previous patent's medium, is the difference enough to enable me to patent my mixture and then sell it as a product in the market or license the patent to producers?

  • So to clarify, you are looking to see if you need to licence the previous patent or just reference it? – Tmanzz122 Nov 24 '15 at 15:27
  • no i am adding a third ingredient to the other guy's patent. so I want to make my own patent based on the "improved' 3 part mixture. – van123 Nov 25 '15 at 18:37
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    If he has an approved independent claim that states "Painting oil + Stone dust" than any time someone is claiming this two, the patent holds - in other words, you can not simply claim it. Since the original expired, you might be allowed a patent on the three components. Suggest to ask a lawyer, or directly the patent office. – Moti Nov 26 '15 at 6:33
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Yes, you could apply for a patent for the new combination. However, it might be refused as being obvious.

The expired patent (P1) which discloses the combination of painting oil and stone dust is prior art. This is true whether P1 is expired or not. Because of this, your invention would need to be non-obvious over P1. Since the only difference is the addition of mineral dust thickener, the key question would be: is it obvious to add the mineral dust thickener to the product of P1.

If there is another document (P2) which suggests that the mineral dust thickener is useful for thickening paints, it would probably be obvious to combine P1 with P2 to arrive at your invention. In other words, your combination would be obvious, and therefore not patentable.

On the other hand, if the mineral dust thickener has never been known to thicken oil-based products (or something like that), the argument could be made that adding it to the combination of P1 is a non-obvious thing to do. Because of this, your product would not be obvious, and so would be patentable.

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