Also, just your point that reminded me ABS is a mix of three plastics, was a great reminder that there's a lot going on that I don't really understand.

Right now I'm buying a 12 quart stock pot I think I'll be begrudgingly practicing the vapor method. I don't have enough acetone to soak my parts in acetone and water. I'll do tests when I have small parts but for now I'm treating very large parts.

But in the meantime, think about why vapor processing would work so well so fast, compared to straight acetone dunking that can take quite a while to get equivalent results of 5mins of vapor work... how/why the breakdown of the butadiene occurs and what that means for the acetone, and whats happening to the styrene .. what is the 'solution' that is created as a result, what is its equilibrium, what is its saturation level, etc...

Anyway - I'll gather up info for you over the next few days. prepare to be underwhelmed.

Can you give a bit more background for where you're coming from making those specific statements? Are you talking about how dunked solids theoretically have a layer of air around them always? Because generally the liquid does still do something to the ABS. Unless it's something special with the acetone-abs melting I assume it's normal solvent-solute interaction from a polar molecule

Acetone vapor doesn't "eat" plastic so far as I'm understanding, it can just condense and melt onto the ABS.

But I understand there's a component I'm probably not understanding. I've seen vapor condensing working well, so there must be something favorable to the vapor- maybe that's what you're talking about.

Sorry if I'm derailing the thread, I am just wondering what I'm not understanding correctly because usually Adrian your posts make immediate sense to me.

I have in the past just splashed acetone on the part to smooth parts, so I'm not sure I fully follow you when you say it's the vapor that does the work.  In the case of dunking, it seems not to be the vapor, but dunking in 100% acetone is just way too aggressive.

Its the vapor of acetone, as molecules break off, that attach to the ABS and eat it. Liquid Acetone doesn't 'do' anything... Dunking something in 100% mix of it is obviously more aggressive, because you have 100% concentration of liquid creating highly concentrated vapor.

Low concentrations will create less vapor.

But its not acetone in a liquid form that is doing anything much to your plastic - its the vapor. Its the same way that Gasoline doesn't burn no matter how hard you try to ignite the liquid - Only the vapor will burn.  And in the same way there needs to be a ratio of air:fuel vapor to have explosive conditions to occur...

So my original point - its not the amount of acetone liquid as a ratio that matters - its how fast and how hard it evaporates that dictates how aggressive it is... hence Alchohol will *accelerate* the process as it encourages faster evaporation and water relative to acetone and alcohol will slow it down. The game is what ratio produces the best time with the best ratio of vapor.

And this is why I said air flow is more important a contributor - as sitting in still air, vapor will clump. In moving air, it has less opportunity to grab some ABS as it sails off into the atmosphere...

I was surprised at the slowness of the mix myself.

I just dropped the parts in a glass jar with the mix and put the lid on then stirred them about every 10 mins.

Oh.. and just to be specific the mix was by volume not weight... not that it changes much.

To clarify, Ronsii, you were dunking the parts in the mixture?

I find it very interesting how though only at 25% water it was very stabilized and only melted slowly.

I personally would like something that limits me from having to use vapor techniques.

To clarify, you said that was Acetone / Water = 75%. I'm unclear if you meant you had a 25% water 75% acetone mixture, or a 1:1.33 ratio of acetone:water.

Temp was 65F
Percentages are acetone

The first sample at 100% is predictable
the second is 75% started to show signs of smoothing and the surface was fairly soft, the third sample had a very small showing of smoothing and the surface was barely softened... as for the last one... it didn't seem to show any effects of acetone at all...
I think if the time were doubled at 75% it would look pretty good.

Its acetone vapour that does the work not liquid acetone incidentally... So alcohol may speed up the process as it will cause increased evaporation compared to water.

The main thing is good ventilation to dissipate the vapour and an air flow to stop it 'pooling'  in valleys in the print.

Water mix will reduce the vapour concentration, but it won't actually reduce the effectiveness of that vapour

So, I was imagining getting the right ratio that you could dunk the part in the mixture, as opposed to dealing with ratios.

I have in the past just splashed acetone on the part to smooth parts, so I'm not sure I fully follow you when you say it's the vapor that does the work.  In the case of dunking, it seems not to be the vapor, but dunking in 100% acetone is just way too aggressive.

The main thing is good ventilation to dissipate the vapour and an air flow to stop it 'pooling'  in valleys in the print.

Water mix will reduce the vapour concentration, but it won't actually reduce the effectiveness of that vapour

In short yes

I didn't want to waste the acetone to try and find out it doesn't work, because it's hard for me to get right now [no car] and I don't feel environmentally good about that. But I was thinking if the acetone mixture wasn't as strong, presumably the piece wouldn't melt too rapidly as it does in regular acetone.

I tried due-diligence and googled a bunch, but heard nothing of it. Just people working on tumblers and vapor smoothing.

Many thanks,
-Tomek