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I am currently stripping 4 Grotz for the next Painting challenge with 91% alcohol, and have about 1/2 a bottle of 91% left. I also have one full bottle of 70% alcohol, and intend to mix together the 91% alcohol with the 70% alcohol. Has anyone tried that? If so, what happens? I want to do it, but I don't want to damage the plastic.

You'll end up with approx 80 odd percent alcohol.

I'm intrigued as to what else you though may happen?!

 Azreal13 wrote:
You'll end up with approx 80 odd percent alcohol.

I'm intrigued as to what else you though may happen?!

I was worried that if there was too much alcohol concentration, the plastic would be damaged.

Crazy, I know...

A little. Alcohol isn't a bad solvent on things like grease, it's unlikely to burn holes in your models if you increase the concentration by a few %

 Azreal13 wrote:
A little. Alcohol isn't a bad solvent on things like grease, it's unlikely to burn holes in your models if you increase the concentration by a few %

Okay thanks!

Is this isopropyl alcohol youre talking about? I've used 100% in the past with no damage to my minis.

 AEIOUMadden wrote:
Is this isopropyl alcohol youre talking about? I've used 100% in the past with no damage to my minis.

Yes, it is.

The question has been answered. But thanks for posting.

Because I'm bored and avoiding doing revision I decided to maths it out

So lets say you have x litres of the 91% alcohol and y litres of the 70% alcohol.

This means you effectively have 0.91*x litres of alcohol being added to 0.7*y litres of alcohol. This gives us 0.91x+0.7y litres of pure alcohol. To get the effective concentration of the alcohol we then divide that by the new total amount of liquid, in this case x+y litres, and then multiply by 100% to turn it from a decimal into a percentage.

So your final concentration will be (0.91x+0.7y)/(x+y)*100% alcohol

Now we just sub in some easy numbers (such as x=y=1 for an equal mixture) and we get 80.5% alcohol, as Azrael said

If you use unequal amounts of liquids (x>y or vice versa), the concentration will increase or decrease respectively.

 A Town Called Malus wrote:
Because I'm bored and avoiding doing revision I decided to maths it out

So lets say you have x litres of the 91% alcohol and y litres of the 70% alcohol.

This means you effectively have 0.91*x litres of alcohol being added to 0.7*y litres of alcohol. This gives us 0.91x+0.7y litres of pure alcohol. To get the effective concentration of the alcohol we then divide that by the new total amount of liquid, in this case x+y litres, and then multiply by 100% to turn it from a decimal into a percentage.

So your final concentration will be (0.91x+0.7y)/(x+y)*100% alcohol

Now we just sub in some easy numbers (such as x=y=1 for an equal mixture) and we get 80.5% alcohol, as Azrael said

If you use unequal amounts of liquids (x>y or vice versa), the concentration will increase or decrease respectively.

Thanks for doing the math.

I recently started using 91% rubbing alcohol for stripping; it does very well on plastic with no damage, it will clean resin as well, but will cause some parts to crack and make the resin rubbery, which is actually good for small resin parts as they won't snap off, just bend.

I'm think the cracking is cause by air bubbles releasing after the alcohol turning the resin rubbery.

 Big Mac wrote:
I recently started using 91% rubbing alcohol for stripping; it does very well on plastic with no damage, it will clean resin as well, but will cause some parts to crack and make the resin rubbery, which is actually good for small resin parts as they won't snap off, just bend.

I'm think the cracking is cause by air bubbles releasing after the alcohol turning the resin rubbery.

When I've used 100% alcohol on FW resin it initially goes soft and then after a while it goes more brittle than it was to begin with.

It CAN have an effect on certain PU resins.
But then, many solvents can do that.
If you want to keep your resins in a not-puddle state, I recommend keeping them away from toluene or MEK, too.

It hasn't harmed any injection moulded styrene bits (conventional model kits/GW plastic figures) I've used it on.

I'm not stripping resin, I'm stripping plastic.

But thanks everyone.