Printing with Copper infused PLA part 2
The copper roof ridge, with natural weathering.
In the previous post, I covered some items I printed in copper infused PLA. 3d-printing-in-copper-model-railroad-details I wanted to take it a step further, and naturally patina the copper (weathering it by oxidation). A little research, and one finds that Uric Acid works well, but it a little gross to handle, so I went with the second option, Ammonia and salt. You don't soak the items in it, but rather you fume the copper. The fumes from the solution cause the copper to oxidize, much as it does in nature. I also wanted to see what would happen if the items fumed for a long time. How green would they get. I wasn't totally satisfied with the roof ridge cap shown above. It had fumed for about 36 hours. I did not measure the amount of salt or ammonia, and I assume different ratios would produce different results, but I am just playing, not trying to do a scientific experiment.
I put about a teaspoon of salt in a plastic container, and printed out some angle pieces to hold the printed parts up above the solution.
I used some raft pieces to make a table to lay the parts on.
Since I had a bunch of copper raft laying around, I ground it up in a blender to use it as a pile of scrap in my junk yard. I put this in a plastic bag, and propped it open to make sure fumes would get in.
I took this picture after 48 hours, and you could tell it was working, lots of copper leaching out into the solution. The next evening, I was tired, didn't even look at it.
After 96 hours, I opened it up to see this. One piece had collapsed under its own weight, and another had warped. I did not know what to think, so I took the parts up to wash off in the sink. I threw a paper towel over the drain to keep the parts from getting away.
Here is the really cool part, there was not much left, the copper had almost completely oxidised away, leaving only some PLA powder.
After it dried, you can really see how little is left.
The scrap in the bag, somehow fared much better, and came out great.
WELL, that got me thinking. How about a test, put a bunch of items in the fuming chamber, and take some out every 12-24 hours, and see how they fair. So, here we go on that...
Printing with Copper infused PLA part 3
I made four sets of buckets and tubs, and placed them in the container with ammonia and salt. Placed the cover on it and let it set for 12 hours.
In 12 hours, the solution was a little blue, but the items did not look like they had oxidized very much.
I rinsed them off, and set them aside to dry. Wet, they were not impressive.
But dry, dang, the looked good.
And after 24 hours, they showed, obviously, more oxidation. Quite impressive.
After 48 hours, the solution was very blue, showing a lot of oxidation had occurred.
No reason to continue the experiment, as the oxidation had deteriorated to the point the parts were falling apart. Once the copper was removed, there was not enough of the PLA left to keep the parts together.
So much of the copper had oxidized away that this copper tub was almost white. It had almost no strength, and was easily crushed. I crushed them up, and threw them in the scrap pile.
This is the 12 hour fumed items, and they look great. If I want a little less patina, I will just fume the products for a shorter time.
The 24 hours fumed items shown here, really show the heavy oxidation. I can't imagine one could need any more patina than this.
I am planning on picking up a rock tumbler later this week, and we will try polishing the copper....