Terracotta or cast copper? Brush, polish, or patina and enjoy!
Introducing Copper Composite HTPLA.  Prints like plastic, but finishes like real metal for beautiful, durable parts from most standard 3D printers.  So many finishing possibilities, but here are some ideas to get you started (see sample Protognomes in product photos):

Heat treat your HTPLA print to survive harsher environments like the hot sun or a warm polishing wheel (more details below).

• Wire Brush to expose metal for future oxidation or a bright, satin finish
• Rock tumble with steel shot for darker, but smooth, shiny look
• Colour Paint part (black for example) to fill recesses with a contrasting
• Polish with a rotary tool, cotton buff, and polishing compound for a bright, mirror finish on high spots (darkens low spots)
• Polish with paper for a clean, smooth, and bright finish with less darkening
• Place in sealed plastic bag to retain moisture. Heat further accelerates reaction.) exposed metal naturally or accelerate with a 50/50 vinegar/hydrogen peroxide mixture saturated with salt.

Try these techniques separately or combine!  Change the order or try something new. If you discover a new technique, make something beautiful, or discover something unexpected, share it!  When you've got that perfect, WOW finish, consider preserving it with a clear coat or brush applicable water-based, food-safe, and dishwasher safe coating like Modge Podge.  Now the only question is, "What will you make?"

Notes and Pointers below.
Heat treating beforehand to firm up HTPLA helps parts hold shape up to near melting (175C). Protect your investment in warm environments or push limits of application by exploring copper's thermal conductivity.  There is not enough copper to be electrically conductive, sintered, or plated, but there is a noticeable difference in weight and heat transfer.

Some application ideas include:

• Faux brick or clay
• Fixtures or hardware
• Knobs or buttons
• Heat sinks or exchangers
• Fine art & sculpture
• Emblems, signage, or trophies
• Pendants or bracelets
• Game pieces, or figurines.  Cosplay

Material data:

• Base resin: HTPLA - Heat Treatable PLA
• Additive: Real Copper Powder
• Particle size: less than 250 micron (0.25mm)
• Low or no Odour
• 2.3 g/cc Approx Density:
• Length (500g): 97m (1.75mm) and 36m (2.85mm)
• Total loss of stiffness (before heat treat): 50-60C (Tg)
• Total loss of stiffness (after heat treat): 150-175C (melting)
• Dimension change (before heat treat): 0% X/Y/Z
• Dimension change (after heat treat): 1.5% shrink X/Y and 1% growth Z typical but please calculate and confirm for your specific print and process

Printer settings:

• Speed: 10-20 mm/s 1st layer, 20-80 mm/s rest of part
• Nozzle Set-point: 185-215C (hottest on 1st layer for best adhesion)
• Nozzle Actual: maintain set-point, reduce speed if less than 
• Nozzle Type: Standard or wear resistant for extended use
• Nozzle Diameter: 0.6mm or larger preferred, 0.4mm okay with 0.25mm minimum for experts
• Layer thickness: 0.15-0.20mm recommended for a balance of quality, reliability, and productivity
• Bed Temperature: Room-60C (over 60C can worsen warp)
• Purple disappearing glue stick or your other favorite PLA surface preparation.

This material has been flow optimised and has less moisture uptake than standard PLA's, however composites are still sometimes more tricky to print depending on hardware and software settings.  The main challenge is to keep mass flow up (larger nozzle + fast speed) and in a single direction (minimal retraction) to avoid heat soak. 

If you are new to exotic filaments, the team at Proto-Pasta have some great tips for you.