| abstract |
A poreless first layer is electroformed on the conductive surface of a mandrel in an electroforming solution containing a substantial amount of a surface active agent. After the mandrel and the first layer are lifted from the solution, small straight pores each having an approximately equal diameter along a length thereof are formed through the first layer defining the front side of a porous electroformed shell. A second layer is deposited on the back side of the first layer in an electroforming solution containing less than the substantial amount of a surface active agent to form the back side of the shell, while undeposited hollow portions are formed in alignment with the straight pores in the first layer in initial formation of the second layer, the hollow portions enlarging to form diametrically enlarged pores through the second layer, the enlarged pores having a diameter which becomes larger toward a surface of the second layer opposite from the first layer. |