White film look when applying paraloid solution to bone

[DE&i]

I often come up against a white film looking appearance when applying a paraloid solution to bone this time of the year. Or to be more exact bringing specimens out of my cold prepping shed into my warm house to finish prepping them.

If quote a very informative paragraph from Harry Pristis of TFF “A working technique for consolidating fossils “it will give you a clearer picture to my issue.

It’s not the slightly unappealing look to it that bothers me.

It’s the slight worry that there may be a detrimental effect on the bone itself.

If anyone has any further information to put my mind at rest I’d be very pleased to hear it.

[Auspex]

I suspect the presence of moisture in the bone. Giving the specimen some drying time under a heat lamp before applying the paraloid should help.

[DE&i]

I suspect the presence of moisture in the bone. Giving the specimen some drying time under a heat lamp before applying the paraloid should help.

I totally agree…but time and time again with my usual “look before you leap approach “my excitement to complete the prepping process got the better of me.

Do you think any harm done to the bone....

[Doctor Mud]

I wouldn't think so.

It would be dependent on preservation and minerals present in the bone e.g sulphides that might react with trapped water to produce dilute acid in the long term.

But if there is any doubt and it's a piece that is not common or is important it would be easy to remove the consolidant with acetone, dry under a heat lamp or at low temperature in a drying oven and re-consolidate. I've used a hair dryer in the past to dry smaller items quickly.

Edited November 8, 2015 by Doctor Mud

[DinoMike]

I totally agree…but time and time again with my usual “look before you leap approach “my excitement to complete the prepping process got the better of me.

Do you think any harm done to the bone....

I'm presuming you used acetone as the solvent to dissolve the paraloid. The white film is caused by a reaction between the acetone & the trapped moisture only. No effect on the fossil. It can be cleared off with plain acetone, if that was what you used in the solution.

[DE&i]

I wouldn't think so.

It would be dependent on preservation and minerals present in the bone e.g sulphides that might react with trapped water to produce dilute acid in the long term.

But if there is any doubt and it's a piece that is not common or is important it would be easy to remove the consolidant with acetone, dry under a heat lamp or at low temperature in a drying oven and re-consolidate. I've used a hair dryer in the past to dry smaller items quickly.

I'm presuming you used acetone as the solvent to dissolve the paraloid. The white film is caused by a reaction between the acetone & the trapped moisture only. No effect on the fossil. It can be cleared off with plain acetone, if that was what you used in the solution.

That’s a relief…panic over ill apply the recommended adjustments over the next couple of days.

Thank you so much.

[ZiggieCie]

Here is one link from the Florida Museum of Natural history on fossil prep that covers water soaked objects.

https://www.flmnh.ufl.edu/vertpaleo/amateur-collector/preparation/

Here is another link I bounced into getting the Florida one.

http://preparation.paleo.amnh.org/assets/BurkeMuseumLabManual_Jan2010b.pdf

Also try using alcohol instead of acetone; it does not react with residual moisture as the acetone. Acetone and moisture create the white haze.

For very wet bone/teeth, that need treatment then they go back to the Elmer's glue type adhesive diluted in water to soak in and dry in a controlled drying chamber.

[oilshale]

It's not only the water inside the fossil, it is also the air humidity.

Acetone has a very low boiling point and readily evaporates. When acetone evaporates, it will cool down and the surface temperature will drop. If there is high air humidity, moisture will condense on the surface creating this whitish appearance / blushing. You might have to substitute acetone by other solvents with higher boiling points (sometimes called retarders) such as isopropanol, butanol or methy ethyl ketone (MEK) .

Avoid working with acetone on rainy days and better work at a warm place (with lower air humidity).

Read more about the 65 / 65 rule:

http://www.woodcentral.com/russ/finish11.shtml

Edited November 9, 2015 by oilshale

[DE&i]

Here is one link from the Florida Museum of Natural history on fossil prep that covers water soaked objects.

https://www.flmnh.ufl.edu/vertpaleo/amateur-collector/preparation/

Here is another link I bounced into getting the Florida one.

http://preparation.paleo.amnh.org/assets/BurkeMuseumLabManual_Jan2010b.pdf

Also try using alcohol instead of acetone; it does not react with residual moisture as the acetone. Acetone and moisture create the white haze.

For very wet bone/teeth, that need treatment then they go back to the Elmer's glue type adhesive diluted in water to soak in and dry in a controlled drying chamber.

Thank you very much didn't realise there was such a wealth of information on this subject out there.

[DE&i]

It's not only the water inside the fossil, it is also the air humidity.

Acetone has a very low boiling point and readily evaporates. When acetone evaporates, it will cool down and the surface temperature will drop. If there is high air humidity, moisture will condense on the surface creating this whitish appearance / blushing. You might have to substitute acetone by other solvents with higher boiling points (sometimes called retarders) such as isopropanol, butanol or methy ethyl ketone (MEK) .

Avoid working with acetone on rainy days and better work at a warm place (with lower air humidity).

Read more about the 65 / 65 rule:

http://www.woodcentral.com/russ/finish11.shtml

I'm learning so much from this thread its great. I might move away from acetone and try and source another solvent to mix with my paraloid beads.

Two more questions : Even when I have a tight lid on my jam jar with solution in it the acetone evaporates after a while. Would an alternative solvent last longer.

[oilshale]

Yep - the higher the boiling point, the lower the evaporation rate will be. Evaporation will be slowed down and drying time will be prolonged (will stay sticky for a longer time)

Thomas