Filling cracks in Missouri Blue Chert?

[RockingRuralMo]

This isn't exactly a carving project, but it didn't quite fit in cabochons or tumbling either, so I apologize if I've struck an irrelevant chord.

I'm using a piece of Missouri Blue Chert to make a business card holder for a friend moving out of state.  It came from the river where we did his going away trip, so I'm pretty well committed to working with this specific stone.

There are some significant cracks in this rock.  It's already shaped and formed, and I think unless it gets dropped what's here should probably going to hold up fine.  So I have about 3 choices:

1) Leave it be and finish it out with the cracks left alone and let it be au natural (I left some surfaces that way, so it may not look amiss.)

2) Try to fill the cracks:  I have

    1) Sodium Silicate

    2) epoxy 330

            I can add mica powder to either of these for added visual interest - I was thinking probably bronze.

I can add mica powder to either of the fillers to add some color and shine.  But as fine as some of these cracks are, I don't know if either of these products will sink down in there, or if I'll just be wasting my time.  I have a rotary tool and could drill them out, but that may break it all together.

Have any of you filled cracks with either of these things?  Did it work?  Were you happy with it?

If I had more time or more of this particular special material I'd be more eager to try stuff out, but since it's the only piece I have, it's kind of important to get it right.  What are your thoughts?

[dillonf]

I've used super glue to fill cracks in thundereggs, and even mend two pieces of a broken thunderegg. It works and holds up great. Large cracks will take several applications. I start with thin then end with thick. You will need to re-polish it after application.

[Peruano]

You probably don't want just any old super glue. I get a super glue in three distinct thicknesses intended for filling cracks, crevices, etc. The original forumula was Hot Stuff; but it comes in a thicker version "Super T" called gap filler; and as "Special T" billed as ultra gap filler. It penetrates tight cracks best if the stone is heated and the glue is backed a bit under a heat lamp as soon as applied. You can mix iron oxide powder in it to disguise the glue line, and can polish it if used on highly polish surfaces.
I buy mine at a real hobby store (not the political one with the lobby) although here in ABQ Thunderbird carries it too. Its made by Satellite City Inc. if you have trouble finding it and need to search the web.

[chris1956]

I agree that because you are limited in time the Super T is probably the way to go.   I was thinking that it might be good to use the thin stuff first (to penetrate as much as possible) and then use the gap filler after the first has cured but you should check to make sure you can use the two together.  Rock shops like Kingsley North offer the Super T and can probably get it to you quickly.  

I have tried to cut and polish the banded chert that I find in northwest Missouri but all the cracks make it difficult.  Even when stabilized with Cactus Juice resin, it still will break apart at times and it is hard to tell what will hold up and what won't until you have stabilized and cut it.  I have gotten to the point where I put most of it in the tumbler and what is good survives and what isn't doesn't.  

[RockingRuralMo]

Thank You, all of you Peruano dillonf and chris1956 . I ordered some thin and some Super T. It will take a few days to get here, but will be worth it to get a result I can be proud of. What do you guys think about the relative wisdom of drilling or not drilling out the cracks? I have some diamond bits and a rotary tool, but not a lot of experience using them. Would drilling in help penetrate the thinner cracks better? Or will the thin glue do its job by itself?

[Peruano]

I suspect no drilling the cracks is necessary unless you think the rock is seriously compromised. I was assuming you were mostly filling cracks for cosmetic reasons. It penetrates really well. We've used it to reduce crazing in opal and on other fragile stones. Occasionally I fill a hole in a particularly pretty piece of pet wood. If you use too much, i.e. create a mound on top of the crack you will pay the price by having to grind/sand it flush and its really hard stuff once dried. When you are really good (probably best on a polished cab) you can hit it with the wheel just as its drying which will rake enough of the host stone into the glue to do an exact match of coloration. Don't try this at home on your mother-in-law's heirloom broach until you have practiced on lesser material.

[Pat]

I’ve used HOT STUFF by Satellite City to fill cracks. You can add powdered host rock or complementary color to it.

Comes in three thicknesses: fast runny, medium runny, and slow. One is labeled “gap filler”.

[RockingRuralMo]

Jun 21, 2023 12:00:04 GMT -5 Peruano said:

 I was assuming you were mostly filling cracks for cosmetic reasons. It penetrates really well.

yes this!  Strictly cosmetic - I think a streak of bronze in the cracks will look cool.  I only processed it down to 300 grit and then stopped until I could decide what to do about the cracks, so I can grind and polish as one unit after the glue comes and I can fill it properly. 

Now to hold my breath until the parcel arrives!  Thank you for your help!  I appreciate it!

[dillonf]

Jun 21, 2023 9:52:57 GMT -5 RockingRuralMo said:

Thank You, all of you Peruano dillonf and chris1956 . I ordered some thin and some Super T. It will take a few days to get here, but will be worth it to get a result I can be proud of. What do you guys think about the relative wisdom of drilling or not drilling out the cracks? I have some diamond bits and a rotary tool, but not a lot of experience using them. Would drilling in help penetrate the thinner cracks better? Or will the thin glue do its job by itself?

The brand I use is star bond.

[vance71975]

Epoxy Resin is what I would do personally

[Fossilman]

Jun 21, 2023 12:07:40 GMT -5 Pat said:

I’ve used HOT STUFF by Satellite City to fill cracks. You can add powdered host rock or complementary color to it.

Comes in three thicknesses: fast runny, medium runny, and slow. One is labeled “gap filler”.

That's what I use also, especially on my fossil work..