On Sat, 26 Mar 2016 20:16:35 -0700, "Bob F"
wrote:

DerbyDad03 wrote:
I'm going to be building something - not plumbing - with 3/4" copper
pipe. As you can see from this image, the pipe is a different "color"
than the fittings. The fittings are bright copper, the pipe itself is
much duller.

Anybody know why that is or more importantly, how to shine up the
pipe so that it matches
the fittings?

http://tinyurl.com/CopperPipeColor

Full link:

http://i440.photobucket.com/albums/q...psxbg1l4fw.jpg

How do they compare after an acid wash?

Wrought copper fittings are c12200 alloy.12200 is 99.90% pure copper
with phosphorous added to deoxidize..
Seamless copper pipe may be manufactured from any of five (5) copper
alloys (C10200, C10300, C10800, C12000, C12200) that all conform to
the chemical composition requirements of alloys containing a minimum
of 99.9% Copper (Cu) and a maximum of 0.04% Phosphorous (P).

About the only difference chemically between the alloys is the amount
of phosphorous remaining in the alloy. The manufacturing process -
drawn vs wrought, will produce varying grain structures, and the
temper will also change the grain structure - which will cause
variation in the colour of the copper as produced. Some of the colour
variability can be reduced by removing the "mill finish" and oxides by
polishing, but different grain structures will reflect light
differently, producing different colour effects.. Soft drawn (flexible
/annealed) copper tubing will more closely match the colour of the
wrought copper fittings available today.

Years ago the majority of copper plumbing fittings more closely
matched the colour of Type K, L, and M hard copper, while today they
more closely match the soft copper, leading me to believe they have
changed the production method used for producing the fittings. I HAVE
noticed the newer fittings are lighter and appear to be softer than
the fittings I grew up with.