Bleaching petrified wood

[mikeinsjc]

Much of the petrified wood from Montana is as black as coal on the inside. It is kind of deceptive, because on the outside water has bleached the whatever out of the rocks surface and you think it is going to be pretty cool inside. They are filthy to cut. The saw oil turns black, the inside of the saw turns black, so I try to wait to cut them until I am ready to change the saw oil.

After I polish the black slabs (sounds like the name for a rock group) I put them in straight bleach for 3-4 days. Wow, what a difference! I would like to post a picture on here but find the procedure too cumbersome for someone that still uses a Razr phone.

Anyway, does anyone have any idea what the bleach is doing chemically? The bleach is not discolored after 4 days so it appears nothing is being removed from the slab, just altered.

PS where is the "attach file" mentioned in the pict upload tutorial? I click "upload file" and nothing seems to happen. Man I hate computers.

[bsky4463]

Hey Mike - I too have bleached petwood collected here in MT. It seems to work very well on wood that has gone thru a carbonization process and doesnt do anything to material that has been silicated. But sorry I do not know specifically the answer to your question.  As you probably already know it just affects the surface of the stone and does not seem to penetrate. Hence I have found it most effective to do it after the grinding and sanding steps but before final polish. Cheers

[parfive]

mikeinsjc said:

PS where is the "attach file" mentioned in the pict upload tutorial? I click "upload file" and nothing seems to happen. Man I hate computers.

I couldn’t find it either a while back. I think that option was disappeared when Cloudy showed up, and it just hasn’t been edited out of the tute.


Tommy ?

[woodman]

You can do the same thing by leaving it lay out in the sun after finial polish. Just takes longer.

[Deleted]

Nov 6, 2018 10:56:41 GMT -5 mikeinsjc said:

PS where is the "attach file" mentioned in the pict upload tutorial? I click "upload file" and nothing seems to happen. Man I hate computers.

What browser are you using? The "Upload File" button should give you a pop-up window into which you can drag the image file or click a button to select it. You have to sign up for Cloudinary before it works, though (see this thread).

[mikeinsjc]

bsky,
I do the bleach after final polish- doesn't seem to make any difference, and the piece still takes a nice polish. I do notice that this wood seems to absorb oil during cutting like a lot of wood does, but the black stuff seems to take in more than others. It seems to clog the bull wheel belts more also.

[oregon]

I offered to post Mike's pics because there is truckloads of 'charcoal' petrified wood here in Oregon as well - never tried bleaching, but might have to.

before and after with the same material  mikeinsjc

 

[bsky4463]

Nov 6, 2018 16:11:09 GMT -5 mikeinsjc said:

bsky,
I do the bleach after final polish- doesn't seem to make any difference, and the piece still takes a nice polish. I do notice that this wood seems to absorb oil during cutting like a lot of wood does, but the black stuff seems to take in more than others. It seems to clog the bull wheel belts more also.

Mike - agreed before or after polish it works...probably even better after polish. I think because the material is not silicated, it is more pourous and absorbs the oil.  I think the gunk on the bull-wheel maybe oil residue. Do you heat the specimens to drive out the oil after you cut?

[mikeinsjc]

bsky,
I have not baked them. It has to be done outside,my friend says, as it really stinks. I figured if baking (my fiend only sets oven at 150)works, so would boiling them in a pot of water on the stove. Glad my wife wasn't home- it really stinks that way too.

I have found some work-arounds that still enable me to get a nice polish. One thing that seems to help- but it may be my imagination- it to wipe the slab with acetone immediately before the bull wheel.

[bsky4463]

mikeinsjc ayup low temp it oozes out. A cheap way to go is an old BBQ, just light one burner on low (low-low) and then offset the pieces on the grill so it is indirect heat. Not a good ID to bake out oil in anything that will used for food consumption IMO..... Tom Yard who builds the Ultimate Grinder (bull wheel) was adamant about getting the oil out to get the best possible shine. He has a cool vacuum oven for this purpose...someday I shall find one!

Another no bake option is soaking in TSP cleaner. I scrub with Simple Green or similar de-greaser and then a 1/4-1/3 cup of TSP per gallon of water and soak them over night and then scrub again with de-greaser... I actually do this with all my slabs before I cab or sell them. Works on wood specimens too, just not as good as baking.

[RWA3006]

Are you guys using plain old bleach, hydrogen peroxide, or something else?

[woodman]

Nov 6, 2018 18:15:33 GMT -5 bsky4463 said:

mikeinsjc ayup low temp it oozes out. A cheap way to go is an old BBQ, just light one burner on low (low-low) and then offset the pieces on the grill so it is indirect heat. Not a good ID to bake out oil in anything that will used for food consumption IMO..... Tom Yard who builds the Ultimate Grinder (bull wheel) was adamant about getting the oil out to get the best possible shine. He has a cool vacuum oven for this purpose...someday I shall find one!

Another no bake option is soaking in TSP cleaner. I scrub with Simple Green or similar de-greaser and then a 1/4-1/3 cup of TSP per gallon of water and soak them over night and then scrub again with de-greaser... I actually do this with all my slabs before I cab or sell them. Works on wood specimens too, just not as good as baking.

Sometime i use a degreaser before baking in an oven in my open tractor shed, I picked up a cheap kitchen stove for just that purpose, for small stuff I have a toaster oven I got a goodwill.  The oil MUST come out before any other work is done.  At least that is what I think!  

[Drummond Island Rocks]

I do not work with pet wood much but after reading the last few posts I think my bowling ball oven is the ideal tool for removing the oil from the slabs. It has heat settings from 125-175 and is made to remove lane oil out of bowling balls. It has a reservoir to hold the oil that drips off. These are basically re-purposed food dehydrators at an inflated price.



This is the oil coming out of one my kids bowling balls.


And this is the oil in the tray when done



Chuck

[mikeinsjc]

rwa3006, I use Clorox germicidal bleach from Lowes, about $4-5/gallon

Drummond, that looks like the perfect thing to treat the slabs. Are those things expensive?

[Drummond Island Rocks]

Nov 7, 2018 12:22:54 GMT -5 mikeinsjc said:

rwa3006, I use Clorox germicidal bleach from Lowes, about $4-5/gallon

Drummond, that looks like the perfect thing to treat the slabs. Are those things expensive?

Yeah they are overpriced because there is a limited market and they have to pay off there tooling. I think I paid about $200 for that one. The company uses the lid and heating element from a food dehydrator and just makes a new base and case to hold the bowling ball. I am sure the dehydrators are cheaper and would work as good or better for slabs.

This is same heating unit on a dehydrator for 1/4 the price. I noticed the temps says 95 to 155 so I may have been wrong in my earlier post.
www.amazon.com/Nesco-FD-60-Snackmaster-Express-Dehydrator/dp/B000LNVUJQ

Chuck

[Deleted]

Nov 6, 2018 22:13:19 GMT -5 RWA3006 said:

Are you guys using plain old bleach, hydrogen peroxide, or something else?

I've used both, but prefer oxygen bleach (aka, Oxi-Clean and similar powdered oxygen bleaches) from the laundry aisle in any grocery store. There is a stronger version sold as Wood Bleach (peroxide bleach + oxalic acid) sold in home improvement stores. There are some oxygen bleaches marketed specifically to rockhounds, though I haven't tried that. Takes longer, but no nasty fumes and less etching on some materials. Agree with sunlight as an even milder option. For any bleaching, you have to live with giving up some of the more intense colors: particularly rich reds, greens, blues and red-browns. I even like the black in some (much better than gray that would result from some harsh bleaching. When just featureless black, bleaching can certainly improve, but I wouldn't bleach only because it turns your oil black (that can be filtered and re-used). As was said, you'd bleach only after you've cut, anyway.

[pauls]

This is interesting, some of the black petrified wood I have found gives off a very organic bitumen smell when cutting, I will have to try this. Different wood, different continent even, and silicified and hard but worth a try.

[woodman]

This a small slab that I bleached by

leaving it out in the sun, it was out for along time maybe a year, I lost track of the time.

[greig]

I suspect the black might be bitumen. It is a hydrocarbon (petroleum) and usually stinks when freshly exposed. I recently read an article for removing bitumen from fossils, whereby they used heated (100 C) biodiesel. Here is the article: web.gps.caltech.edu/~als/research-articles/2015/19-ss-42rice-et-al.pdf