Questions on using paraloid

[Calli99]

Hi there,

 

I picked up a couple of pieces of flaky shale with some bivalves and ammonites from Whitby a couple of days ago and want to use a paraloid-B72 solution to consolidate them. I’ve never done this before so am hoping someone can share some advice. 

 

At the moment I’ve got them soaking in water to remove any salt and in a day or two I’ll remove them to dry naturally. I want to do a bit of prep with some dental tools and then consolidate.

 

My main question is do you think I should soak them in the paraloid or brush it on?

In terms of dilution I want to buy a premixed bottle as I live in a small flat and want to avoid stinking of acetone as much as possible. The lowest concentration I can find is 5% wt/vol, would this be suitable for submersion/brushing on?

If submerging, how deeply does the specimen need to preserved and can I submerge more than one specimen in one container? I can see myself having to buy a lot of solution for this...

 

Sorry for all the questions, I’ve found it quite difficult to find clear answers online.

Here are the pieces in question

 

[Ptychodus04]

5% should be fine for consolidation. It is a little more concentrated than I usually use but may actually work better to hold in the cracks. I would soak them. You can soak as many as will fit without touching each other. They only need to be fully submerged. I would place the pieces in the container and pour in the paraloid until you have about 1cm of solution above your tallest specimen. Soak until the bubbles stop coming out of the specimens and then place on a cardboard flat to dry. They may stick to the cardboard a bit but you can remove any cardboard residue by applying acetone with a rag and rubbing gently. Also, if there's too much sheen for your liking, you can wipe the surface with acetone to remove some of the surface layer of plastic.

[hadrosauridae]

First, I'm no expert, but I can share my paraloid experience to maybe help you.

 

I dont know what your cost for he finished paraloid solution is but you should start by looking into the cost of buying acetone and compare it first.  If you are needing enough to soak the fossil, you will need quite a bit.  5% solution SOUNDS good, but I will have to go find my notes to see what % I ended up prefering.  The good deal with this type of consolidate is that you can make it what you want; very thin for penetration or thick for a surface glue.

 

Now, as to brush or soak, that will depend entirely on the stability of your item.  If it is known to be long term stabile and you just want to avoid surface cracking, spalling, etc, then a brush on of thin solution will be fine.  If the matrix is known to become crumbly, fragile, etc over time then a full soak would be in order. 

 

For your current stabilizing effort, I would recommend soaking it for several weeks.  Use distilled water and change it out every few days.  If it has deep saltwater penetration, it could take a long time to get it out.  Week might not be enough, but you should consult with local fossil collectors about their experience.  I'm sure you know the result of salt crystal growth in your specimen if allowed to happen.

 

Forgot to include- making your own paraloid solution is easy and doesnt create any odors.  Your solution would be in sealed containers anyway, so dont let that route scare you off.  You will need to make sure the soaking container is stabile with acetone.  Dont pick a type of plastic that will be dissolved!

Edited April 22, 2021 by hadrosauridae

[Calli99]

9 minutes ago, Ptychodus04 said:

5% should be fine for consolidation. It is a little more concentrated than I usually use but may actually work better to hold in the cracks. I would soak them. You can soak as many as will fit without touching each other. They only need to be fully submerged. I would place the pieces in the container and pour in the paraloid until you have about 1cm of solution above your tallest specimen. Soak until the bubbles stop coming out of the specimens and then place on a cardboard flat to dry. They may stick to the cardboard a bit but you can remove any cardboard residue by applying acetone with a rag and rubbing gently. Also, if there's too much sheen for your liking, you can wipe the surface with acetone to remove some of the surface layer of plastic.

 

Thank you so much for this advice. It’s just what I was looking for. A slightly odd follow up question: How do you dispose of the remaining paraloid left in the container? And if using a glass tray for example, does it clean up easy or is best to use something disposable like an aluminium tray?

 

14 minutes ago, hadrosauridae said:

First, I'm no expert, but I can share my paraloid experience to maybe help you.

 

I dont know what your cost for he finished paraloid solution is but you should start by looking into the cost of buying acetone and compare it first.  If you are needing enough to soak the fossil, you will need quite a bit.  5% solution SOUNDS good, but I will have to go find my notes to see what % I ended up prefering.  The good deal with this type of consolidate is that you can make it what you want; very thin for penetration or thick for a surface glue.

 

Now, as to brush or soak, that will depend entirely on the stability of your item.  If it is known to be long term stabile and you just want to avoid surface cracking, spalling, etc, then a brush on of thin solution will be fine.  If the matrix is known to become crumbly, fragile, etc over time then a full soak would be in order. 

 

For your current stabilizing effort, I would recommend soaking it for several weeks.  Use distilled water and change it out every few days.  If it has deep saltwater penetration, it could take a long time to get it out.  Week might not be enough, but you should consult with local fossil collectors about their experience.  I'm sure you know the result of salt crystal growth in your specimen if allowed to happen.

 

Forgot to include- making your own paraloid solution is easy and doesnt create any odors.  Your solution would be in sealed containers anyway, so dont let that route scare you off.  You will need to make sure the soaking container is stabile with acetone.  Dont pick a type of plastic that will be dissolved!

 

Thank you so much for your advice. I believe this type of matrix is know to crumble fairly quickly, certainly handling it too much feels risky, therefore I will definitely soak them.

 

I’m actually not sure quite how much exposure to salt these specimens had as we split the shale to reveal them. I will soak them for a while longer than planned and dry them slowly in a bag just to be safe.

 

Good point about the soaking container!

[Ptychodus04]

Make sure your specimens are thoroughly dry or the Paraloid will turn white from trapped moisture. You can put them in the oven on low heat to help them once they appear dry.

 

I would use a disposable container for the soak. Unless the container is completely smooth, the Paraloid will stick to it horribly.

 

As for the leftovers, use a funnel to pour it back into the original container. If the lid seals well, it will keep indefinitely.

 

I agree with @hadrosauridae, the acetone smell is not extreme. If you have a balcony, do your soak outside and you have no fume issues at all.

[Wrangellian]

12 hours ago, hadrosauridae said:

I dont know what your cost for he finished paraloid solution is but you should start by looking into the cost of buying acetone and compare it first.  If you are needing enough to soak the fossil, you will need quite a bit.  5% solution SOUNDS good, but I will have to go find my notes to see what % I ended up prefering.  The good deal with this type of consolidate is that you can make it what you want; very thin for penetration or thick for a surface glue.

 

Now, as to brush or soak, that will depend entirely on the stability of your item.  If it is known to be long term stabile and you just want to avoid surface cracking, spalling, etc, then a brush on of thin solution will be fine.  If the matrix is known to become crumbly, fragile, etc over time then a full soak would be in order. 

...

Forgot to include- making your own paraloid solution is easy and doesnt create any odors.  Your solution would be in sealed containers anyway, so dont let that route scare you off.  You will need to make sure the soaking container is stabile with acetone.  Dont pick a type of plastic that will be dissolved!

Agreed, but I will add that there is a 3rd option to brushing vs. soaking: what I do is mix up some (Acryloid in my case) in a small jar with aluminum foil lining the lid, at whatever consistency you need (not too thick or thin) and put some into a Fineline applicator (available at hobby places), and use that to squeeze it in to the cracks in the rock - after it has been cleaned and dried thoroughly of course.

The benefit is that you don't need to mix up a huge amount of solution as you would to submerge the whole rock, and while there will be some excess dribbling down the outside of the rock, there is not as much of it to clean with acetone afterward. Just a Q-tip dipped in acetone.

The Fineline is not affected by the acetone solution, it seems to withstand long term and seals well enough that I can leave it in there when I'm done using it, until it runs out, and I've had no problems. The cap does not seal perfectly tight as I've noticed leakage when I take it out into the sun while collecting. (Better indoors)

Your rock doesn't look too fragile/crumbly as to need submersion in consolidant. My local stuff is crumbly shale, worse than yours I think, and I mainly use the Fineline to stabilize it. Sometimes it's tricky, but submerging it would be tricky too, I think.

 

Edited April 23, 2021 by Wrangellian

[Thomas.Dodson]

Not much to add that the others haven't said but I'd reiterate that it is easy, clean, and low smell to mix your own. It's no doubt cheaper and will last you longer too.

 

1 hour ago, Wrangellian said:

Your rock doesn't look too fragile/crumbly as to need submersion in consolidant. My local stuff is crumbly shale, worse than yours I think, and I mainly use the Fineline to stabilize it. Sometimes it's tricky, but submerging it would be tricky too, I think.

It might be prudent to go full submersion anyway since the preservation looks pyritic. Better to keep all the moisture out at the start.

[Calli99]

13 hours ago, Ptychodus04 said:

Make sure your specimens are thoroughly dry or the Paraloid will turn white from trapped moisture. You can put them in the oven on low heat to help them once they appear dry.

 

I would use a disposable container for the soak. Unless the container is completely smooth, the Paraloid will stick to it horribly.

 

As for the leftovers, use a funnel to pour it back into the original container. If the lid seals well, it will keep indefinitely.

 

I agree with @hadrosauridae, the acetone smell is not extreme. If you have a balcony, do your soak outside and you have no fume issues at all.

Thanks for the advice. The 'balcony' is only about 2 inches deep but with the doors open wide it'll have to do.

 

1 hour ago, Wrangellian said:

Agreed, but I will add that there is a 3rd option to brushing vs. soaking: what I do is mix up some (Acryloid in my case) in a small jar with aluminum foil lining the lid, at whatever consistency you need (not too thick or thin) and put some into a Fineline applicator (available at hobby places), and use that to squeeze it in to the cracks in the rock - after it has been cleaned and dried thoroughly of course.

The benefit is that you don't need to mix up a huge amount of solution as you would to submerge the whole rock, and while there will be some excess dribbling down the outside of the rock, there is not as much of it to clean with acetone afterward. Just a Q-tip dipped in acetone.

The Fineline is not affected by the acetone solution, it seems to withstand long term and seals well enough that I can leave it in there when I'm done using it, until it runs out, and I've had no problems. The cap does not seal perfectly tight as I've noticed leakage when I take it out into the sun while collecting. (Better indoors)

Your rock doesn't look too fragile/crumbly as to need submersion in consolidant. My local stuff is crumbly shale, worse than yours I think, and I mainly use the Fineline to stabilize it. Sometimes it's tricky, but submerging it would be tricky too, I think.

 

My concern with this method is that I might easily miss some spots. I think I will try this with the belemnite piece though as it seems less fragile and could be good practice for this sort of application. I also like that not all the specimen would be coated and it would be more delicate to apply than a brush.

19 minutes ago, Thomas.Dodson said:

Not much to add that the others haven't said but I'd reiterate that it is easy, clean, and low smell to mix your own. It's no doubt cheaper and will last you longer too.

 

It might be prudent to go full submersion anyway since the preservation looks pyritic. Better to keep all the moisture out at the start.

I've already ordered the premixed stuff now but with everyones reassurance here I will definitely mix my own next time.

Yes there is some pyrite in there. I've heard mixed things about the usefulness of paraloid in terms of preventing pyrite decay but this could be a useful experiment as my current method is just thorough soak, dry and silica packets.

 

I think that I will try submersion for the larger pieces with the ammonites and bivalves and finline applicator for the belemnite and a couple smaller pieces not pictured. Thanks everyone for your help, you're all wonderful 

[Wrangellian]

With the kind of rock you're dealing with, it probably won't matter if you miss a few spots, as long as you get the majority / main cracks, it will hold together. That is if you're not planning on letting schoolkids manhandle it repeatedly or anything like that... then you might want to use the submersion method!

The other benefit of this method is you can apply and then watch it soak into the crack, and if you figure it needs more, add more, until the seeping in stops or slows down. (You don't need to overdo it.) You'll know you've made too thick a mixture if you see that it's not seeping in.

Edited April 23, 2021 by Wrangellian

[Wrangellian]

Here's what it often looks like when I'm stabilizing a fragile shale fossil... I've got clamps of various sizes (and clothespins ) to hold parts together. Often a gap wants to separate and the clamp helps close the gap. It only needs to be on there long enough for the glue to set, which is not long with this stuff. Longer for larger fossils with larger/deeper gaps.

It was not easy to get this pic - using the tripod and timer for hands free. Excuse the messy background! But you can see my various jars for acetone and glue solution there.

 

Another reason to not dunk or brush a fossil in glue is the fossil itself might be too fragile even to clean off afterward with a q-tip in acetone. You might impair the detail on a delicate/detailed fossil. Or it might be just plain difficult to get into all the crevices etc.

Here's an example of a fossil I would not have wanted to clean afterward if I had dunked it! Of course this one I had to reassemble anyway, so dunking it was not an option. You can see some glue spots but these were not as hard to remove as it would have been to clean glue from the whole thing. I guess all this will be readily apparent to anyone once they get to this point, but I make this presentation just in case.

 

 

Edited April 24, 2021 by Wrangellian