For my latest architectural commission I suggested my clients the use of patinated brass to represent a specific material finish in the proposed building design, since they liked the idea.. We went ahead with it!
I particularly like this process and find it quite fascinating how the metal reacts to the chemicals. Specially the stage before the brass is totally patinated, half way through the process.. it goes through an unstable moment.. that was the point which I aiming for to remove the sheets from the acid. This 'half way" method makes the material 'roughly' or badly patinated (in the good sense though) giving the effect of random metallic toned reflections with some subtle blueish and red, brown tinted blotches.. Purposely avoiding the consistently patinated look throughout.. Which is of course another option! Depending on the requirements and purposes.. The full patination method is also a great option to represent bronze finished details in general, not just in models..
I hope the photos not only show what I try to describe above, but also the process from start to finish. I had to adapt the original cad drawings received by the architects, then sent it to be etched at 4D modelshop who were very helpful in delivering these on a very tight schedule! Once the cad drawings are modified and sent I receive the sheets in brass at 0.38mm thickness by request and the ideal thickness for my purpose. Then the patination process starts.. 3x trays were needed (acid resistant trays used for photography) 1 filled with rust cleaner (watered down), 1 with water and 1 with antique fluid (the patinating stuff!). 1st I dip the sheet in the rust cleaner of a couple of minutes rubbing in gently with a super soft brush to avoid scratching the metal.. this helps to clean any grease as this will show in the end result (finger prints..), 2nd I rinse it and dip it in water again roughly 2 minutes.. rubbing it gently on both sides, then rinse and dip it in patenting fluid for about 5 to 6 minutes to achieve the rugged reflective look.. if I wanted it fully patinated, this could be achieved in around 10 minutes. After patinating the sheets I dipped it one last time in water to clean off any patination fluid excess and rinsed it.. then cleaned it very well with much tissue until it's all dry.. left it to rest for 10 minutes +- and then treated it with 'liberon' Jade oil rubbed on a tissue, which seals the metal sheet and also prevents the patination process from being active in the longer run.. which is also an interesting thought! But not for this occasion..
I hope this post is constructive and educational as I personally don't see a lot of explanations or tutorials on how this particular process is done and I think it's something that it's relatively easy enough for anyone to do even from their own home. It's extremely effective and I really enjoy experimenting with this stuff!