Mechanics of applying glue to hairline cracks

[SteveE]

I'm going to attempt to clean up and glue the stromatolite I posted about the other day (yes, its a stromatolite).   This will be my first rock gluing adventure.  I've read several threads here, and watched a bunch of youtube vids.  None of them really focuses on the actual process of consolidating unbroken rocks that are starting to come apart with a network of baby cracks.   Please help?

 

I have paraloid pellets andsuperglue (liquid form).     I assume one goes along the crack with a dropper or brush and the glue magically gets down into the crack by gravity or capillary action?  Is there a way to tell if it was effective (without actually trying to torque the rock at the crack)?   How about removing the visible "seam" ?   For larger pieces with multiple hairline cracks do you treat them one by one or something else?

 

Some of this rock's "domes" are also loose.  I'll do those with gel superglue once the base is stabilized.

 

I might decide to make a vertical cut and maybe polish a face.  Is that even possible with a rock trying to break apart?

 

Feel free to answer the unasked questions too, and bonus points if you know of a video that zeros in on consolidation of a weak but unbroken samples.  Thanks!  

Edited March 1, 2022 by SteveE

[Mark Kmiecik]

Are the cracks visible on the backside of the specimen? If so, just touch a small drop (pinhead size or smaller) of the thin crazy glue at several places along each crack, or at the junctions if the cracks form a grid. Capillary action will suck it deep enough if the specimen is up to about an inch thick. If you're working with a specimen that is thicker than one inch you'll need to apply more glue rather quickly so it gets as far in as possible. I've had some specimens less than an inch thick have it come all the way through and out onto the specimen itself, so be careful not to give it too much. The easiest way to learn the technique is to break some non-fossil rocks and practice gluing them back together. Three or four seams and you'll get the hang of it. Paraloid dissolved in 100% alcohol will get down into the seams as well. Alcohol takes longer to evaporate than acetone so it has a bit more time to get down in there. If you have to apply from the front side you will get some on the surface. Either way, if you get some on the face of the specimen you can remove the crazy glue or Paraloid with acetone by dabbing the surface or brushing with a medium stiff paint brush like the cheap trim brushes you get at hardware stores if the fossil is sturdy enough to handle it.

 

If the pieces have come apart completely you must remove any loose material from the surfaces that fit together and always remember to leave an obtuse angle in the place where you will glue the next piece. If you create an acute angle, the next piece will not fit into the crack 9 out of 10 times

 

Good luck -- and let us know how it turns out. Of course, others may have better methods than these, so wait for some additional help before you start.

Edited March 1, 2022 by Mark Kmiecik
added info

[Randyw]

For consolidating cracks like that I use a thin super glue. It’s about as thin as water so it easily wicks into the cracks. Caution! I once glued an oreodont skull to my hand becuase i didnt notice it was wicking all the way through LOL!

i like the loctite long neck for wicking into cracks.

[Ptychodus04]

I use Starbond superglue at times. It comes with a very small applicator that will allow minute applications of glue. This is a rare use for me. I typically drop Paraloid into the cracks with impunity. Once they are sealed up, I abraid the Paraloid away. This provides a heartier bond than super glue. Cyanoacrylate is strong but brittle. Paraloid is more forgiving of lateral stresses. Also, Paraloid is substantially easier to remove than superglue.

[SteveE]

FYI, the slab

14 hours ago, Mark Kmiecik said:

If you're working with a specimen that is thicker than one inch you'll need to apply more glue rather quickly so it gets as far in as possible. I've had some specimens less than an inch thick have it come all the way through and out onto the specimen itself, so be careful not to give it too much. The easiest way to learn the technique is to break some non-fossil rocks and practice gluing them back together. Three or four seams and you'll get the hang of it. Paraloid dissolved in 100% alcohol will get down into the seams as well.

 

 

The slab is roughly 4x12x14 inches;  Thanks very much for this reply, I'll give the alcohol-paraloid a try.