I Used Birchwood-Casey to Blacken Those 5" Screws

It is theoretically something that you brush on.  But in this case I found a plastic lunch meat container and filled the container above the screws.  Then I rolled them around with tweezers and left them in there for a couple hours.

You will not mistake this for black anodized but they are really black and for optical purposes better than black anodized.

I wish that I was thinking of this stuff a couple years ago when I needed to touch up an American Arms PX-22.  This was a black finished zinc frame .22.  It just did not make sense to get this professionally refinished like I did with my Browning Hi-Power.  Cerakote made a paint it yourself kit which produced an okay finish (okay that might be a statement about the person doing it).  I suspect I could  have done a better job with Birchwood-Casey and a Q-tip.

Anyway for about $10 I created an optically black set of screws.  The thumbnuts going on are already black plastic so this will give what I could not find for sale: black 5" thumbscrews.

Looking at them in brighter light, they are closer to dark brown than black but still very optically unreflective.

I have not epoxied the thumbnuts in position yet but because the smallest quantity I could buy was 10, I realized that putting two of them on each screw meant more purchase with my fingers. 

Curiously, two thumbnuts may obviate the need for epoxy.  The second one seems to hold the other one in position.   I will try it in the application and see if it works without epoxy.

It seems I do not need epoxy.

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Spanish Permablue.