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How to prepare Paraloid b-72 for use as an adhesive and consolidant


McHorse

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Heres how I prepare Paraloid b-72 for use as an adhesive and consolidant. Generally I use the approximate mixing ratios shown below which have been taken from a paper written by Amy Davidson and Gregory W. Brown called Paraloid b-72: Practical tips for the vertebrate fossil preparator, which can be found here: https://www.academia.edu/1237393/Paraloid_B-72_Practical_Tips_for_the_Vertebrate_Fossil_Preparator

Approximate mixing ratios:

Paraloid ratios.tiff

However, if you want to create a solution of a known weight by volume percentage such as 20% (w/v) theres a trick. Since weight by volume solutions are worked out as the mass of the solid in the final volume of the solution, you need to know the volume of your final solution.

For example if you had a 100ml bottle that you want to fill with a 20(w/v) solution of Paraloid what you would do is:

1) fill the bottle with 100ml of liquid.

2) mark on the bottle where the top of the liquid is.

3) weigh out the amount of Paraloid, which in this case would be 20g = (20/100)x(100 mL) as

Mass of Paraloid = (Percentage of solution/100)x( final volume of the solution).

4) add the Paraloid to the bottle and fill with the solvent (acetone in this case) up to the 100ml mark.

Say you wanted to make 2 litres of a 5% solution of Paraloid. You would follow the above steps replacing the 100ml with 2000ml = 2 litres. The mass of Paraloid would be (5/100)x(2000) = 100g.

Note: it is important to keep you units consistent so if your volume is in mL your mass will be in grams. If your volume is in litres your mass will be in kilograms.

Another form of concentration is a weight/ weight percentage, which is the percent by mass of the final solution where:

Concentration of solution %(w/w) = (mass of solute)/(mass of final solution)

This is a bit more complicated as you don't know how much volume of solvent to add or what the final volume would be. This technique is usually used to make big batches of the solution and is probably not all that useful for the weekend warrior.

Hope this helps someone.

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Thanks for the post McHorse!!

I use B-72 quite often, and have distributed a few with these exact instructions!

The only thing I have to add would be Pearson's Square. This can be very useful if using pre-mixed batches of a known %.

This is used for diluting pre-mixed batches.

I keep my paraloid in a quart container at 50% and dilute down as needed

A = Stock Solution %

B = New Desired Solution %

C = Diluent %

D = New Solution %

X = Part of stock needed for new batch

Y = Part of diluent needed for new batch

X = B - C

Y = A - B

D = X + Y

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