Mixing waxes - come on all you chemists ...

[Phil Pascoe]

If I were to mix 50/50 a wax with a melting point of 50c with one that melted at 60c, would I end up with one that melted at 55c?

 

[sunnybob]

5 degrees c is the normal plus or minus tolerance of any heating thermostat. Thats such a small difference it would be very difficult to accurately confirm which temp it melted at. is it really essential to know?
or is it an evening brain teaser?

If its a brain teaser, I reckon 57.5 is the winning number.

 

[Phil Pascoe]

It was only an example - it could as easily have been 100c and 200c, would that come out at 150c?
I'm just waiting for someone to say 50c and 60c - no, it'll still be 60c because ... or it'll be 52c because ...

 

[n0legs]

I think you would see a separation of the two components with each one melting at their respective temperatures.
Years ago before we went cold pour resin to fill the cable joints we used hot black pitch.
The two most commonly used were A57 and A66.
A57 was liquid at approx 120c whereas the A66 was liquid at 155c (IIRC), anyway you could tell when the apprentice had put the wrong compound in the wrong bucket. You had lumps. We then had to either risk continue heating the bucket and possibly burning the A57 or throw it away.
Maybe a bit of kitchen chemistry is in order Phil

 

[sunnybob]

The bigger the difference, the more likely it is to catch fire.
Apart from water, most liquids will eventually combust.
If one melts a 100 degrees before the other, the lower melting point one will burst into flames before the higher goes liquid.
therefore my second answer is .... 42

 

[bugbear]

If I were to mix 50/50 a wax with a melting point of 50c with one that melted at 60c, would I end up with one that melted at 55c?

A quick google turned up some academic papers on the subject; the very fact that they exist is enough to tell you "it's complicated"

BugBear

 

[ED65]

Damnit I thought this was going to be an easy one but you actually did want a chemist (hammer)

I'm just waiting for someone to say 50c and 60c - no, it'll still be 60c because ...

A few things do actually work that way (most likely the lower temp though) but from what I've picked up piecemeal in relation to candle making this isn't one of them. The wax with the higher melting point has a 'tempering' effect, as long as it is uniformly spread throughout the mixture.

Are you aiming for a specific melting point Phil, or just above a certain temp?

 

[Phil Pascoe]

I was wondering if I could add beeswax, carnauba or whatever to microcrystalline, so it would give a nicer polish but keep its high resistance to fingerprinting. Just because it's not done commercially doesn't mean it can't be done.

 

[mind_the_goat]

What's the significance of the melting temperature? Unless you intend to apply it in it's molten state.
I don't think you would get any chemical changes just by mixing, you'd just have a mixture containing 2 or 3 different substances which are likely to retain their own properties. I assume you want to heat them up to make mixing easier but you may find that the substances would separate out due to different densities. I would suggest heating to somewhere below melting point to reduce viscosity but not to liquefy them. As mentioned you may also need to be aware of volatile gasses being released.

 

[Phil Pascoe]

Beeswax marks easily because it softens at blood temperature. Microcrystalline doesn't give as nice a polish as some others, hence I'm trying to find a mid line.

 

[ED65]

I was wondering if I could add beeswax, carnauba or whatever to microcrystalline, so it would give a nicer polish but keep its high resistance to fingerprinting. Just because it's not done commercially doesn't mean it can't be done.

Er, it is done commercially.

But you can make a polish based on beeswax that's more resistant to fingerprinting simply by blending it with enough carnauba or candelilla. That is in essence the reason those are used as additives in the first place, the lesser tendency to marking is an aspect of the increased durability they provide.

The main reason this isn't done as much commercially is almost certainly down to cost.

 

[chaoticbob]

Bugbear is right - it's much more complicated than averaging the two 'melting points'. Think of lead - tin solder, which liquifies at a lower temperature than either lead or tin (183C for the eutectic mixture). What actually happens is to do with the balance of affinities of the molecular constituents in the mix for their own kind and for other species. As well as some other gubbins to tedious to go into. Trust me I'm a doctor! (of chemical physics).
Coincidentally I'm looking to make up a home-brew finishing wax myself (hence my visit to this part of the board) - I was going to start with beeswax/carnauba blends taking a purely empirical 'suck it and see' approach. But now I want to know about this microcrystalline wax - is it available in pure form? I should Google I suppose,
Regards, Robin

 

[Phil Pascoe]

http://www.ebay.co.uk/itm/Microcrystall ... 2096548422? And
http://stores.ebay.co.uk/oliverbrown-ch ... 581&_pgn=2
I used for carnauba and beeswax. Warrior Warehouse is local to me, and their pure turps in 250mls was as just about as cheap as I could find, even in 2 1/2Ltr and 5Ltrs. I've always used a beeswax/carnauba/turps polish, but wanted to try a m/c mix. One problem I can see is melting it - it has a melting point of 72c (of course, it might just dissolve in turps - I've not tried it yet.)
Eutectics had occurred to me. I had thought that these mixes had undoubtedly been been trialed by commercial firms, but I've not seen any unusual mixes marketed.

 

[ED65]

But metal alloys are a different beast entirely Robin. A mixture of two or more metals interact to form, in effect, a new metal entirely. That's not at all what happens with other materials.

'Miscible mixtures' for want of a better term have a much more obvious, and linear, interaction because no new material is formed, it is merely an intimate mixture of the components. Basically, when you add something with a high melting point to something with a low melting point you get a melting point in between. That's (nearly always?) how it works with plastics, resins, waxes and almost all fats, a rare exception being something including cocoa butter.

This is assuming thorough blending of course.

 

[Phil Pascoe]

It is all info I'm trying to find. Logic (or at least, my logic ) would suggest that the melting point is somewhere in between, but where? The melting point of beeswax is about 64c and of m/c about 72c - interestingly carnauba is 82c (pure waxes, of course) So if you were aiming for a polish that didn't mark at hand heat carnauba might seem more logical than m/c. - yet that is (or seems to be) the main advantage of m/c polishes.

 

[ED65]

Have any of those wee jars that hotels sometimes have jam in Phil? I've managed to build up a small supply of those which I use just for things like this, little batches of mixed paint, oil/varnish blends etc.

If I had all three waxes available what I'd do is make up tiny batches of paste wax in three of them, pure microcrystalline, pure beeswax and a mix of beeswax and carnauba (at least 10% but not as much as 40%), let them set and then try them out side by side on a single board sealed with a light coat of shellac. That'll tell you much in short order and give you a starting point from which to go.

Microcrystalline wax by itself suits some people (as beeswax did and still does it must be said), but if the pure white colour is a problem it can be tinted with oil-based stains or oil paint without noticeably affecting its wearing characteristics

 

[Phil Pascoe]

I've just done one 25/25/50 by weight m/c/carnauba/turps - it's worked well, I'll have to try it in a few different ways.

 

[chaoticbob]

Thanks for the links to suppliers of m/c wax Phil - I ordered up a block which arrived a couple of days ago. Apologies if the reference to solder was unilluminating - I was just trying to reinforce the point that you can't, in principle, predict the melting point of a mixture by averaging the melting points of the components. I could argue about metals and waxes being 'entirely different beasts' but this is hardly the place for a discussion about the thermodynamics of phase transitions!
Just out of interest I did a couple of kitchen chemistry experiments measuring the cooling curves of the beeswax and a 50/50 mix of beeswax and the m/c:

.

The pure beeswax shows a pretty clear transition in the range 63-64.5 degrees, but the mixture seems to be more complicated - my gut feeling is that a mixture of phases forms during solidification. Probably not relevant, but it all data I suppose... and it keeps me from actually finishing a project and realising that woodworking is harder than physics!

I'll be trying your 25/25/50 mix, thanks for that.
Regards Robin

 

[Phil Pascoe]

"I was just trying to reinforce the point that you can't, in principle, predict the melting point of a mixture by averaging the melting points of the components."
Yes. That was the point of the OP - it's easy to presume, and I know better. I might try a straight m/c next.