FMF - Friends of Minerals Forum, discussion and message board

[Peter Megaw]

In commentlng on a crumbly rosasite matrix it occurred to me this should be copied here for those with similar problems with porous, crumbly and disintegrating matrix.

Crumbly matrix will continue to crumble unless you stabilize it...which is easy to do. I have used this on hundreds of wulfenite specimens perched on punky crumbly gossan matrix. It also works well to keep competent gossanous matrix from shedding.

DO THIS BEFORE YOU SATURATE THE MATRIX WITH WATER DURING CLEANING OR DO IT AFTER YOU LET THE PIECE DRY COMPLETELY.

YOU CAN CLEAN ALSO AS THE FINAL STAGE HERE IF YOU'RE CAREFUL.

AS ALWAYS, IF YOU HAVE A REJECT LUMP TO PRACTISE ON YOU CAN GET A FEEL FOR HOW IT WILL BEHAVE BEFORE YOU TREAT YOUR PRIZED SPECIMEN(S)

ALSO, MAKE A NOTE IN YOUR CATALOG THAT THE MATRIX IS "STABILIZED WITH WHITE GLUE"

Get an Elmer's (or other brand of water soluble white glue) applicator bottle that is 1/4- 1/3rd full of glue. Top off with hot water...leaving enough space (1/2" or 1 cm) at the top so you can easily shake the liquid and mix it thoroughly. Your goal is to have a 25-35% highly liquid solution of dilute glue...so agitate until you're sure it's well mixed. Use the applicator tip to gently flood the matrix...the tip will allow you to avoid getting any (much) on the crystals. Don't over-flood the specimen...this can turn the matrix to mush. Take your spray bottle and gently spray the crystals or rosasite balls to remove any glue and/or brush dings. This gets tricky if you completely saturate the specimen either with glue or the final spray off. Lay a piece of aluminum foil where you can leave the piece to dry out for a couple of days. Position the specimen so that any excess glue solution that drains out of the matrix drains AWAY from the crystals. Once dry the specimen should be substantially more solid and coherent than before and you can gently peel the foil off if it has stuck to the specimen.

You may be able to do some trimming prior to stabilizing but if the matrix is too crumbly don't even try...stabilize first. Once stabilized you can soak just the area you want to remove in water for 20-30 minutes...enough to rewet the glue. You can then trim off (often just with your fingers) the part you want gone and then set aside to dry. The glue will reset and you're done.

[Peter Megaw]

In some cases cyanoacrylate glue (superglue or crazyglue) also works well to stabilize matrix and/or keep fractures from propagating. This is effectively irreversible so it's a MUCH bigger commitment than white glue.

Cyanoacrylate comes in a range of viscosities...from extremely fluid (hot) to very viscous (and even gap filling)...so be sure you know which type you're working with. Viscous glue will not penetrate or soak in well and fluid glue will not fill gaps.

You can use it in much the same way as dilute white glue...and if you're really serious you can get an "accelerator" that makes it set very quickly. Unlike white glue it is hard to remove and the solvents used to do so can be nasty and flammable. And...you can glue yourself to the piece ...or glue the piece to a table if you're not careful.

Note also that cyanoacrylate is highly volatile and evaporates quickly...this means fluid glue becomes more viscous over time (sometimes not even very much time) ...to the point of getting syrupy. If you really care about the specimen, start with a fresh tube. The big bottles you can get seem like a bargain but unless you're going to use them all at once they will get syrupy before you can use them up!

Again, in the interests of full disclosure, make a note that you stabilized the piece with cyanoacrylate...someday someone may want to do more work on the piece and it helps to know what chemistry is appropriate to undo what you did

[Peter Megaw]

A final comment on stabilizing crumbly matrix.

If your problem is a crumbly gossanous matrix that sheds dust on your shelves or in your drawers the dilute white glue technique works well to stop or reduce this.

Spray starch does too...and some find it less problematic in a humid environment than dilute white glue.

As far as I know silverfish won't eat your specimens to get at the starch

[Pete Richards]

Excellent comments, Peter.

I have also used a commercial wood hardener, meant to soak into punky wood to stabilize it. I used it because I already had it - it's probably basically a fancy thin version of white glue anyway.

One other possibility is to thin Duco cement with acetone - it works but it is also very flammable and more permanent than the white glue approach.

[Joseph DOliveira]

I have used a slightly more dilute version of this white glue mixture to stabilize fossil fish from the Kemmerer, Wyoming area. It really helps to reduce the chalky residue that you get from the volcanic ash matrix.

[Jesse Fisher]

Another note on cyanoacrylate - I've used the fluid, penetrating variety to good effect to stabilize crumbly and fractured matrix on many Rogerley specimens. It spreads and penetrates very quickly and if you are not careful it is easy to glue the specimen to your fingers, but unlike the more viscous types of cyanoacrylate, it tends not to leave residule glue ponded on the surface of the specimen.

To extend the life of a bottle or tube, cap it good, place in a ziplock plastic baggie and store in the freezer.

Also, make sure the specimen is completely dry before applying cyanoarcylate. If there is any water in cracks of the specimen, the glue will leave a white residue on the surface that is difficult to get rid of without an air abrasive unit.

[vicen]

Why did you use PVA to consolidate the minerals?

Personally, I'm a fan of the Paraloid B-72 in different concentrations of acetone and/or ethyl alcohol. I have been working with Paraloid B-72 for nearly 18 years and I have fantastic results. It can ONLY be used with specimens which are absolutely dry.
To make sure that the inside of the specimen is consolidated, it is good practise to begin with a dilute solution (or even just solvent) and follow increasing the concentration solutions. This thin solution will help the more concentrated solution to penetrate.
For simple consolidation I would use first a 5% Paraloid B-72 solution in acetone for deep penetration followed, after about one hour, by a 10% solution of the same. I will use a polypropylene pipette, as brushing will not penetrate deeply enough. Sometimes it is recommended soak the specimen. If the specimen is needed in the future for examination, the Paraloid B72 can be removed with acetone by brushing the surface polymer without causing damage.
Sometimes I will add glass beads or glass thread or matrix powder to the mixture.

Some bibliography on Paraloid B-72: Koob (1986), Down et al. (1996), Podany et al. (2001)

[lluis]

Dear Vicen

I suppose that is a question of habits
Paraloid is a stuff widely used in museums, by for particulars is not that easy to find.
White glue is common for all, easy to use, non flammable (a great difference with Paraloid and acetone, that are very flammable), non toxic (another difference with acetone), and many times get same results. Specially with stabilizing matrix.
Paraloid would be far better for repairing or stabilizing iron things (old weapons, for instance...). But to stabilizing, the old white glue, Elmer's glue, is easy, innocuous and far inexpensive.
Being both removable, well, I see no advantages on one over the other.
I use both...but for separate uses.
Stabilizing, always white glue (vinyl acetate aqueous....)

With best wishes

Lluís (chemist)

[Jordi Fabre]

Recommended reading: Repairing mineral specimens

[vicen]

Lluís

I cannot believe that Paraloid is not easy to find! Pass me your address and I will send you some grams that will give you adhesive for long time!

Ok, "white glue is common for all, easy to use, non flammable (a great difference with Paraloid and acetone, that are very flammable), non toxic (another difference with acetone), and many times get same results." but you cannot talk about toxicity when you are talking about stabilising a mineral. I normally work with small containers (60-120ml maximum) not much acetone! Ventilation is important.

I have been using Paraloid to conserve and prepare fossils, minerals and rocks and no "iron things".

3 things to consider about white glues (Polyvinyl Acetate co-polymer):
* they have to dry out before are effective
* they will shrinks
* its penetration is dubious

Vicen

[lluis]

Hi Vicen

Paraloid is easy to find....in tones.
Trouble is to find it in small quantities (yes, paying as much for a kg than for a bag of 25 kg).. But things are as they are.... :-(

On the other side, vinyl acetate is done with colloid protector vinyl alcohol....or with a tensioactive.
And even more, in different sizes.
The big sized ones, with many steepens, would penetrate not too well and will let many material out.
Small size, filtered, will penetrate.
And tensioactive ones by sure that will penetrate (maybe no so quick as Paraloid in acetone, by sure; water is far viscous than acetone....)
Shrinking, well, being so dilute, they do not shrink. And during my days (28 years...) in textile industry, I have never seen a film of vinyl acetate shrinking.... But, well, that is my past experience and maybe in the rest of time anytime I could see it. I do not expect. nevertheless, see that....

I will send a private mail not to bore the rest of list...

With best wishes and many thanks for the offer!

Lluís

[lluis]

Trial

[cascaillou]

I wouldn't use cyanoacrylate glue on minerals as it emits vapors that forms white veils on clean surfaces (such as crystal facets) making these much less lustrous. There are solvent-free glues that act just as fast as cyanoacrylate but without the vapors.