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Running Amber


charliemaine
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13 hours ago, charliemaine said:

I don't think I would cook in it again but would like to use it to measure things.

Once you clean it thoroughly, you should feel confident cooking in it again. Never trust a beaker to measure volume, however. That is what a graduated cylinder is for.

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6 hours ago, joerobson said:

True.  It can.  However sorting the resin for color and controlling the temperature and weight loss creates options.  This is how I separate my dark and pale amber varnishes.  The resin for dark amber starts at a coffee color.

I certainly agree regarding the effects of controlling the temperature and weight loss.  I used to sort amber pieces based on colour but in recent years have been lazy especially when using amber from suppliers like Kremer where there always seems to be a mixture.

My impression is that time taken to reach the temperature where the amber begins to run is of some importance.  In my case slowly heating the amber up to what should be a running temperature has resulted in the resin sweating and not running, ultimately producing a carbonised result that is useless.  It might also be that heating up the amber too quickly has certain negative outcomes in terms of transparency and lightness of colour.

When attempting to run mixtures of amber resin, it seems that some pieces run more readily than others.  Getting everything to run requires pushing the temperature higher which in turn produces a darker end result.  Once I get the majority of a mixture running, I try to keep everything bubbling away at that temperature, cooking no more than maybe 15 minutes.   Cooking beyond this pushes the colour of the run resin towards an increasingly cold looking and deeper/darker brown.  (You can check the development of colour via placing blobs of resin on some glass, noting how the colour changes with cooking time.  Be aware though that thermal shock can/will readily crack the glass so try to somehow keep the glass reasonably warm!)  The downside of this is that you end up with lumps of amber that haven't run in amongst the run resin.  In the spirit of laziness I haven't worried too much about this as these lumps are in the minority and get filtered out during filtering of the final varnish. 

Re fire mentioned by charliemaine, the very few instances of volatiles igniting that I have experienced have all involved the use some form of wind shield.  I would also make sure that there is at least some breeze present when running amber..

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From my understanding , fossil amber is a fully polymerised resin which is why it is difficult to dissolve in oil etc... By heating all your doing is decomposing the resin( ie ruining it) . It has no relation to the initial amber when cooked like this .But would end up more like a hard copal varnish. If you wanted a film of amber you would dissolve straight into something like Chloroform or Dichloromethane ,then it would be basically a spirit type varnish.

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7 hours ago, fiddlecollector said:

From my understanding , fossil amber is a fully polymerised resin which is why it is difficult to dissolve in oil etc... By heating all your doing is decomposing the resin( ie ruining it) . It has no relation to the initial amber when cooked like this .But would end up more like a hard copal varnish. If you wanted a film of amber you would dissolve straight into something like Chloroform or Dichloromethane ,then it would be basically a spirit type varnish.

When cooking colophony down for color, either too long or too hot, does this also decompose the resin? It seems some makers cook there colophony down until it is black like coal in order to achieve a darker color. I often wondered if this is ruining the resin.

What do you consider a safe temperature when cooking a colohony/linseed oil varnish? I've been saving some very nice colophony from Portugal and would like to cook a batch of oil varnish using it, but I don't want it too dark.

Also I'll be running some fossil copal (Madagascar) soon and I would like to keep it as pale as possible. My understanding is that fossil copal doesn't take as much heat to run as amber. I hope I can keep the temperature down and prevent it from darkening too much.

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The chemical reactions involved in cooking colophony are complex, and results vary by temperature and time as you note. I have gotten excellent results cooking for 200 hours at 200 C, but this produces a very rich color (though perfectly transparent), and it seems you're looking for a light or colorless product. You don't have to cook it long at all. If you were to weigh out your oil and colophony in the desired ratio by mass, combine them, then gradually raise the temperature to 200C and hold it there for two hours, you would get a very pale varnish. You would want to neutralize the acidity of the colophony (primarily abietic acid) somewhat - calcium oxide is the typical choice. What you end up with is a calcium rosinate as the calcium ions fuse to the abietic acid molecules in the hot solution. However, calcium rosinates have long term water solubility issues. This can be avoided by using a different metal oxide, such a zinc or manganese. These have a more neutral pH and do not neutralize the acid as effectively. Therefore the better way to make the rosinate of those metals is by the liquid process, which I have written about extensively. The resulting resin is neutralized in this way and bonded to a more stable ion than calcium. 

Edit - note that if you are going to neutralize the colophony (thereby producing rosinate), you do so to the molten resin alone before adding oil. You can either allow the rosinate to cool, then cook into oil, or you can heat the oil and add the hot oil slowly to the hot resin.

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2 minutes ago, JacksonMaberry said:

The chemical reactions involved in cooking colophony are complex, and results vary by temperature and time as you note. I have gotten excellent results cooking for 200 hours at 200 C, but this produces a very rich color (though perfectly transparent), and it seems you're looking for a light or colorless product. You don't have to cook it long at all. If you were to weigh out your oil and colophony in the desired ratio by mass, combine them, then gradually raise the temperature to 200C and hold it there for two hours, you would get a very pale varnish. You would want to neutralize the acidity of the colophony (primarily abietic acid) somewhat - calcium oxide is the typical choice. What you end up with is a calcium rosinate as the calcium ions fuse to the abietic acid molecules in the hot solution. However, calcium rosinates have long term water solubility issues. This can be avoided by using a different metal oxide, such a zinc or manganese. These have a more neutral pH and do not neutralize the acid as effectively. Therefore the better way to make the rosinate of those metals is by the liquid process, which I have written about extensively. The resulting resin is neutralized in this way and bonded to a more stable ion than calcium. 

Thank you

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8 minutes ago, JacksonMaberry said:

That makes sense - the main ingredient is a strong base. Glad you got it clean. 

Still leary about cooking in it again. You sure it's OK? That would make one helluva bad day if it broke while cooking on an open flame. I hadn't even considered cooking in a beaker until I watched the Edgar video. I don't have a background in chemistry.

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8 minutes ago, charliemaine said:

Still leary about cooking in it again. You sure it's OK? That would make one helluva bad day if it broke while cooking on an open flame. I hadn't even considered cooking in a beaker until I watched the Edgar video. I don't have a background in chemistry.

Always inspect glassware for chips, cracks, bubbles, or other flaws before use. Like someone else said above, you might consider getting rid of the wind shield. If the glass has been carefully inspected and does not have any physical/structural flaws, you may continue to use it without reservation. 

 

Edit - at some point I'd suggest ditching the open flame in favor of a good laboratory hot plate with built in magnetic stirrer. Safer and better. 

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19 minutes ago, JacksonMaberry said:

Always inspect glassware for chips, cracks, bubbles, or other flaws before use. Like someone else said above, you might consider getting rid of the wind shield. If the glass has been carefully inspected and does not have any physical/structural flaws, you may continue to use it without reservation. 

 

Edit - at some point I'd suggest ditching the open flame in favor of a good laboratory hot plate with built in magnetic stirrer. Safer and better. 

Can you recommend one that is hot enough? 

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I think that it is worth noting that the harder organic resins: amber, the copals...Zanzibar,

Congo, etc. were the rage of the age for woodworkers in the 1700's.  Yet the violin makers of the time chose to stick with the established tradition of using pine resin based varnishes on their instruments.

on we go,

Joe

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1 minute ago, joerobson said:

I think that it is worth noting that the harder organic resins: amber, the copals...Zanzibar,

Congo, etc. were the rage of the age for woodworkers in the 1700's.  Yet the violin makers of the time chose to stick with the established tradition of using pine resin based varnishes on their instruments.

on we go,

Joe

And for good reason I suspect! Thanks Joe!

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15 hours ago, JacksonMaberry said:

To cheaply clean lab glass that has oils or resins hardened on - prepare a solution of 5% KOH and 5% isopropanol in water. Soak the glassware overnight. The oils and resins will saponify and can be scrubbed off more easily.

Another thing which can work well is to place the cookware in a closed container with ordinary household ammonia, and leave it to fumigate for several days. I first learned of this from a barbecue grill manufacturer, when I asked how to remove stubborn burned-on food and grease. Their suggestion for a container large enough to hold the grill parts was a large plastic garbage bag, closing the end with a twist-tie or zip-tie.

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21 minutes ago, joerobson said:

I think that it is worth noting that the harder organic resins: amber, the copals...Zanzibar,

Congo, etc. were the rage of the age for woodworkers in the 1700's.  Yet the violin makers of the time chose to stick with the established tradition of using pine resin based varnishes on their instruments.

on we go,

Joe

While pinaceae resins are an identified common feature in old instrument varnishes, amber presence is yet to be dismissed.  I'm not advocating the use of amber in any form, just that, at this stage, no one appears to know one way or the other... 

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32 minutes ago, John Harte said:

While pinaceae resins are an identified common feature in old instrument varnishes, amber presence is yet to be dismissed.  I'm not advocating the use of amber in any form, just that, at this stage, no one appears to know one way or the other... 

We keep our eyes and options open...how else do we learn?

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