How to actually use Paraloid B-72 and the like, for a total newbie

[daveola]

I am not particularly a fossil collector, I have come across some cheap Spinosaurus teeth.

I know they probably aren't particularly interesting from a collection standpoint, but I think they are quite fantastic.

I want to make them as hard and protected as possible, for the sake of ornamentation.  I hope that isn't heresy.

Point being, I am comfortable with using products that may not be appropriate for fossils that are of higher value and going on a shelf.

I've read some about Paraloid B-72, and that it can be mixed (at a ratio of 1 paraloid/10 solvent??) with something like acetone.

If I do that, would I want to just soak the fossil in the solution to maximize the penetration?  How long should that be done?  And I see that in drying I have to be careful since the wet fossil can end up bonding to whatever it's sitting on.  Any other suggestions?

And thanks for your time!

And I can't figure out how to get notified of replies once I've posted, so I'm adding this to turn on notifications.

[daveola]

I see that Harry Pristis on the pinned "Preserving Fossils" recommends:

"Ideally, you would submerge the dry specimen in this consolidant for a brief time (say 15-30 seconds, or until the specimen stops fizzing). Set each wet specimen aside to dry on cardboard (I use beer-flats)."

But wouldn't that be dangerous in terms of bonding to the cardboard?  Is there any way to get deeper penetration into the fossil?

 

[izak_]

2 hours ago, daveola said:

I see that Harry Pristis on the pinned "Preserving Fossils" recommends:

"Ideally, you would submerge the dry specimen in this consolidant for a brief time (say 15-30 seconds, or until the specimen stops fizzing). Set each wet specimen aside to dry on cardboard (I use beer-flats)."

But wouldn't that be dangerous in terms of bonding to the cardboard?  Is there any way to get deeper penetration into the fossil?

 

I personally don't use that technique. I usually paint it on with a brush.

 

But when using that technique, I presume you would let the acetone evaporate off and then sit it on the cardboard.

Once the acetone is evaporated, you don't have to worry about it bonding to anything else because the paraloid is only soluble in acetone (if you use acetone). You don't need it to get soaked up into the fossil, you only need it to be on the surface, so that there is a coating of the paraloid over the fossil. That is how I do it, others may do it differently.

The ratio of acetone and paraloid depends on the fossil and what state its in.

[Ptychodus04]

The cardboard soaks up the solution so fast that there's not enough time for the specimen to bond to the flat (unless you are using a very thick solution.

 

You do in fact want the plastic to penetrate as deeply into the fossil as possible for the very best consolidation. The plastic only protects the part of the fossil where it actually is, so a shallow surface application doesn't help the center of the specimen (if it needs consolidation). Soaking is the best method for this. Make sure the teeth have not been repaired prior to doing this though. The soak method will release the bond of most glued due to the acetone in solution. Brushing on is the only option if a repair is present.

 

I prefer a much thinner solution than 10:1. For soaking I like 20:1 or even 30:1. This allows the acetone to carry the plastic deeper into the specimen. If you have to brush the solution on I use a 50:1 ratio.

 

All this being said, most teeth are pretty stable on their own. Unless pieces look like they are going to fall off, consolidation may not be necessary at all.

[daveola]

7 hours ago, Ptychodus04 said:

All this being said, most teeth are pretty stable on their own. Unless pieces look like they are going to fall off, consolidation may not be necessary at all.

 

I am looking at consolidation (and soaking) to try to make the fossils stronger, since I want to do more than just store them on a shelf.  I was hoping that I could just soak them long enough to get the plastic to soak completely through the teeth to make them much stronger - or is this an unlikely hope?

[Ptychodus04]

5 minutes ago, daveola said:

 

I am looking at consolidation (and soaking) to try to make the fossils stronger, since I want to do more than just store them on a shelf.  I was hoping that I could just soak them long enough to get the plastic to soak completely through the teeth to make them much stronger - or is this an unlikely hope?

 

Soak them until the bubbles stop coming out and you should be in good shape.

[Harry Pristis]

Ptychodus04 has it right.  The following is from my MY PROFILE / ABOUT ME page on  TFF:

I usually heat specimens with an infra-red lamp to drive off moisture just before dipping the fossil. I do this with all sorts of fossils, and have never had one damaged by the heating. The untreated specimen is always at least as wet at the relative humidity of the air around it, I surmise. (A microwave oven may be as effective, but I've only dried glass beads for my air-abrasive unit.) Residual moisture may cause a white film to develop on the surface of a fossil after dipping in the consolidant.

 

Here's how the white film forms: As the acetone in the consolidant evaporates, the temperature at the surface of the specimen chills abruptly, lowering the dew-point at which ambient water vapor condenses.

 

And, that's my theory -- that the white film has two potential sources: residual interstitial moisture and ambient humidity condensing at the surface chilled by evaporation.

   Think about a plastic bag of food placed into a freezer, where frost is moisture and bag is the film of consolidant. Frost can form on either or both sizes of the plastic bag, inside frost from moisture in the food and outside frost from atmospheric moisture.

   My solution is heating the specimen to drive off residual moisture, and consolidating while it is warm to increase the dew-point at the specimen's surface, inhibiting condensation as the acetone boils off.

Do NOT heat the acetone solution directly. The acetone solution will get warm after dipping a number of heated fossils. You must have good ventilation to deal with the fumes!

I use a long-jawed forceps -- ten-inch tweezers, really -- to dip and/or retreive the fossils from the jar.

Ideally, you would submerge the dry specimen in this consolidant for a brief time (say 10-30 seconds, or until the specimen stops fizzing). Set each wet specimen aside to dry on cardboard (I use a beer-flat because that cardboard is absorbant and doesn't readily stick to the fossil).

To avoid pooling of consolidant which may drain from a bone, I rotate the bone once or twice in the first minute or two after placing it on the cardboard. This helps avoid a "drip-bead" of consolidant near the lowest point of the bone.

For a specimen too thick to be submerged, you can use a turkey-baster to flood the difficult areas. I treated an adult mammoth tibia that, because of its size, I dried in the Florida sun, then used the baster to pump consolidant into every opening of the bone.

I use a RubberMaid-type container to hold the consolidant for this basting step - that plastic seems to be impervious to the acetone. Get 'em at your local dollar-store.

Acetone evaporates very quickly. Replenish the consolidant mixture with a bit of acetone if you are using it on many specimens. Store it in a tightly sealed glass jar. Even if some acetone evaporates away between uses (it always does, it seems), you can reconstitute the solution by replacing the acetone.

Acetone is a nasty solvent. The fumes are explosive. The fumes are toxic. The liquid penetrates the skin-blood barrier. It's best to use gloves. Use in a well-ventilated area.
--------------Harry Pristis

 

[daveola]

What about the paraloid B72 liquid that can be found fairly cheap on ebay?

 

Does anyone know if this is in water or acetone?  And what kind of concentration it might be at?

[JohnBrewer]

21 hours ago, daveola said:

What about the paraloid B72 liquid that can be found fairly cheap on ebay?

 

Does anyone know if this is in water or acetone?  And what kind of concentration it might be at?

If you're in the EU I can help. Just drop me a pm. 

[Malcolmt]

1 to 10 in my opinion is much to viscous for what you are looking to do. As a consolidant I would try 1 to 20 and if it is not penetrating then add more acetone.

[Castle Rock]

Malcomt- on another post HERE on this Forum, Ptychodus4 is suggesting a (consolident) mixture of 1: 50 PVA to acetone.  I am preparing to use PVA (Vinapas) on small, thin bones in matrix from the Smoky Hill (NIobrara) Chalk.  Your thoughts would be welcomed!  Dave 

[Malcolmt]

I do not collect vertebrates so my work is mostly on trilos and crinoids. 20 to 1 works good for them. I would expect that at 1 to 50 that you would get better penetration of bone. With a trilo I am only looking at consolidating fractions of a millimeter into the matrix and exoskeleton. What I am trying to accomplish is to consolidate an exoskeleton that is at risk of flaking off. I do not generally soak but rather paint it on or use a syringe to inject into crannies.

[Drenthe]

I am hoping to use a solution to consolidate somewhat wet bone specimens that I find in sand bars. Many of them are partially submerged and will fall apart if I disturb them. Would like to make them strong enough for me to remove them. 

[jdiaz55]

On 7/7/2017 at 6:02 AM, Ptychodus04 said:

The cardboard soaks up the solution so fast that there's not enough time for the specimen to bond to the flat (unless you are using a very thick solution.

 

You do in fact want the plastic to penetrate as deeply into the fossil as possible for the very best consolidation. The plastic only protects the part of the fossil where it actually is, so a shallow surface application doesn't help the center of the specimen (if it needs consolidation). Soaking is the best method for this. Make sure the teeth have not been repaired prior to doing this though. The soak method will release the bond of most glued due to the acetone in solution. Brushing on is the only option if a repair is present.

 

I prefer a much thinner solution than 10:1. For soaking I like 20:1 or even 30:1. This allows the acetone to carry the plastic deeper into the specimen. If you have to brush the solution on I use a 50:1 ratio.

 

All this being said, most teeth are pretty stable on their own. Unless pieces look like they are going to fall off, consolidation may not be necessary at all.

To get that ratio, is it done by weight? I'm seeing a lot of different methods to creating the right ratio. So how much acetone would be needed to add to how much paraloid to get that 50:1?

 

And how long is the shelf life of the acetone/paraloid dilute after its been dissolved?

[Ptychodus04]

7 hours ago, jdiaz55 said:

To get that ratio, is it done by weight? I'm seeing a lot of different methods to creating the right ratio. So how much acetone would be needed to add to how much paraloid to get that 50:1?

 

And how long is the shelf life of the acetone/paraloid dilute after its been dissolved?

It's less exact than one would believe. I use volume for my mix. There's no limit to the time you can store a solution. The longer it sits, the more acetone will evaporate causing it to thicken. You can simply add more acetone when this happens.