|
Post by Hard Rock Cafe on Oct 14, 2012 16:10:12 GMT -5
Daniel (deb193redux) came to visit for the Celebration of Agates show in July and we tried to cook some agate. Unfortunately, he brought the wrong acid and I didn't get it done until recently. He's done a lot of experimenting and can chime in. The basic procedure is that you soak the agate in sugar water (or honey water) and then let it dry. Once dry, boil it in a strong acid (I used sulfuric). Be sure to have baking soda or some other neutralizer handy! The acid turns the sugar to carbon, thus making it black. If you don't want to use acid, you can try it in an oven. Here is the "before" picture that Daniel took: Here is "after", dry: Here is "after", wet: Some agates work better than others. The clear and white agates have the most potential for improved contrast. These came out brown and white, rather than the "tuxedo agate" black and white that we were hoping for. The process can be repeated, I believe. I'll post results if I do it again. Thanks again for the lesson and the agates Daniel!!! Chuck
|
|
|
Post by Pat on Oct 14, 2012 17:43:11 GMT -5
Interesting! I just heard yesterday that you can put a butane torch to mookaite to turn it red. On my way to try it now....
|
|
|
Post by deb193redux on Oct 14, 2012 17:49:17 GMT -5
Yeah, there was egg on my face when I drove hundreds of miles with a bottle of sodium silicate instead of the bottle of sulfuric acid.
One innovation Chuck did was to use the grade of sulfuric acid in drain cleaner. I thinkit turned out OK, and it is cheaper and can be gotten without paying shipping.
The two lace agates in the bottom corner should get better contrast when you start to sand. The whites should get whiter.
The one on the top left is really tuxedo.
Great meeting and visiting.
|
|
|
Post by gingerkid on Oct 14, 2012 19:37:42 GMT -5
Can really see the difference after cooking them. Look great!
|
|
hubrocks
fully equipped rock polisher
Member since April 2011
Posts: 1,563
|
Post by hubrocks on Oct 14, 2012 20:41:43 GMT -5
That's a good thing to learn.........Hub
|
|
|
Post by Hard Rock Cafe on Oct 15, 2012 8:18:21 GMT -5
Thanks for the clarification on the tuxedo Daniel! You know better than I! The back side has some darker bands, which I think is due to different porosity. It's hard to tell from the photos, but the back has some additional partial bands that are not on the front.
Lessons learned: 1. I would definitely wear long chemical gloves if I were to do it again. I had a minor splash as I moved the slabs around and the acid burned a small hole in my shirt sleeve as well as my hand.
2. Do this outside and stand upwind! The process really gives off a lot of fumes.
3. My Walmart hot plate didn't quite get hot enough to boil the acid, although it got hot enough to cook the sugar.
4. My Pyrex casserole dish either had a hidden crack or developed a crack that opened up in the process. Result: sulfuric acid draining into my hot plate. Fortunately I had unplugged it by then because I was done. I had also put a sheet of plywood on the ground under the hot plate, which caught most of the spill.
Chuck
|
|
Deleted
Deleted Member
Member since January 1970
Posts: 0
|
Post by Deleted on Oct 15, 2012 10:02:37 GMT -5
I was going to ask you about the hazards and concerns about boiling sulfuric acid, but I think you answered them. Sounds a bit scary, I think I will try the baking approach. I assume you still soak the agate in a sugar solution before baking?
Good luck,
Tim
|
|
|
Post by Hard Rock Cafe on Oct 15, 2012 11:06:22 GMT -5
Yes, that's right, Tim. You need to soak the agate in a sugar solution because it's the sugar that carbonizes (turns black). We tried a weaker acid, but it didn't change anything. The acid is manageable if you're careful and comfortable working with it. Otherwise, the oven should work. Use a slow ramp up and hold at 350 to 400, then slowly cool. You may want to put the slabs in sand before putting them in the oven so that the heat is absorbed more evenly. Here's an interesting link related to the process: www.uni-regensburg.de/Fakultaeten/nat_Fak_IV/Organische_Chemie/Didaktik/Keusch/D-sugar_coal-e.htmChuck
|
|