perfessor
sage
Reged: 12/30/07
Posts: 499
Loc: Northern Illinois
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This subject was touched on in another thread, but I don't want to derail it there - so I'll derail it here!
I picked up an old Jaegers kit at a bargain price, and bought a GotGrit kit which included Gugolz pitch. So I have a pound or so of burgundy pitch that must be 30 or 40 years old. Is it usable?
Along a similar tangent, there's an ad on the 'bay for some leftover pitch, of unknown age.
Can these be reconstituted with turpentine, tested for hardness, and used? Or is it best to buy new?
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Tom
"Don't always know what I'm talkin about"
8" f/7
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mark cowan
Vendor (Obsidian Optics)
Reged: 06/03/05
Posts: 2156
Loc: salem, OR
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If stored so that it can't lose solvents it should stay good indefinitely. If it still smells like pitch it's likely good, you can always test it, temper it with turpentine, and use it if it tests good.
Best,
Mark
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RossSackett
professor emeritus
Reged: 08/17/07
Posts: 691
Loc: Memphis, TN
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My biased opinion: pitch is cheap. Old pitch isn't worth the risk.
Ross
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"A craftsman relies on science when the state of knowledge allows it, tradition and experience when it does not, and makes art whenever he can."
12 scopes from 4.25 to 18" and a 24" in progress. 12 ATM awards. Webpage: http://stardazed.com/ Some more scope pix at http://www.flickr.com/photos/8315630@N04/
Anagrams: Amateur astronomer = A mature moon-starer; Dobsonian maker = Debonair as monk
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Mark Harry
Post Laureate
Reged: 09/05/05
Posts: 3121
Loc: Northeast
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I have pitch that I use for polishing and figuring that averages ~15 years old. (Gugolz) Don't know about the burgandy stuff.
I like the old stuff I'm using. I know how it's supposed to act, so actions are predictable.
M.
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So many projects, so little time!
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perfessor
sage
Reged: 12/30/07
Posts: 499
Loc: Northern Illinois
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Hmmm - sounds like we got one yes, one no, one maybe. 
I guess I'll melt a bit and test it. Thanks for the advice, all!
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Tom
"Don't always know what I'm talkin about"
8" f/7
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JohnH
professor emeritus
Reged: 10/04/05
Posts: 734
Loc: vancouver near the wilds of B...
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Pitch, as long as it is kept clean, is useable.
It DOES lose its softness with age, as anyone who has tired to reuse an old pitch lap has found.
One batch I have is in chunks in old Crown sealer jars. It all melted and smelled fine, just needed sone beeswax and a few tsp of turrpentine to make it more flexible.
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perfessor
sage
Reged: 12/30/07
Posts: 499
Loc: Northern Illinois
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I'm not familiar with adding beeswax. What's the guidelines on that?
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Tom
"Don't always know what I'm talkin about"
8" f/7
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JohnH
professor emeritus
Reged: 10/04/05
Posts: 734
Loc: vancouver near the wilds of B...
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The pitch is usually quite brittle. Take a piece into your fist and warm it up and it usually cracks it. The beeswax "tempers" it and makes it less fragile.
Up to around 10% is what most books suggest. Other people add rosin to theirs for similar effect.
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Mark Harry
Post Laureate
Reged: 09/05/05
Posts: 3121
Loc: Northeast
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Rosin -HARDENS- pitch, probably what you -DON'T- want to do. To soften it, usually terpentine (fresh, not something old and discolored) is used to replace the natural solvents.
I don't use beeswax because it's not resilient, like correctly tempered pitch is. In some optical shops, beeswax is used to block up small parts on metal based tooling.
Mark
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So many projects, so little time!
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kfrederick
professor emeritus
Reged: 02/01/08
Posts: 659
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you could mix it with some softer pitch . donot like the smell of terpentine
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ed_turco
member
Reged: 08/29/09
Posts: 26
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I've saved laps for twenty YEARS by putting them in the freezer, so nothing dares evaporate from the pitch. These laps are as good as the day I made them.
If these were left at room temperature, they would have turned into cement by this time.
By the way, in this economy, pitch isn't cheap any more. Nothing else is either.
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mark cowan
Vendor (Obsidian Optics)
Reged: 06/03/05
Posts: 2156
Loc: salem, OR
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Quote:
you could mix it with some softer pitch . donot like the smell of terpentine
Different grades and process smell differently - the pure gum turp you can get at art supply shops tempers pitch very well and has a nice bouquet, perhaps a bit forward but it wears well. 
Best,
Mark
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perfessor
sage
Reged: 12/30/07
Posts: 499
Loc: Northern Illinois
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OK, next question: Can I mix burgundy and Gugolz? I have about a pound of each, and need to make a 10" lap.
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Tom
"Don't always know what I'm talkin about"
8" f/7
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Mark Harry
Post Laureate
Reged: 09/05/05
Posts: 3121
Loc: Northeast
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I keep my used pitch in a large tupperware container on the shelf next to the grinding tools. Have had no problem with solvents evaporating at all. It seems as long as the temps are moderately cool, this is a satisfactory way of storing used pitch, too. Glad you chimed in, Ed!
Mark
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So many projects, so little time!
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ed_turco
member
Reged: 08/29/09
Posts: 26
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Glad you noticed my comment on pitch. Most ATM's think I am crazy!
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Mark Harry
Post Laureate
Reged: 09/05/05
Posts: 3121
Loc: Northeast
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"Most ATM's think I am crazy! "
***************
I get the same feeling here! Most of my pitch is around 15 years old or more. (before they changed the recipe)
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So many projects, so little time!
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Glig
sage
Reged: 10/02/05
Posts: 370
Loc: Baltimore, MD
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In a sealed container, Gugolz will not change. Out in the open, Gugolz will outgas and get harder. I've had some laps that I left out out so long they they nearly turned into stone.
That's why I'm switching to Acculap. Doesn't outgas, doesn't change hardness if you leave them out.
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Richard Caldwell
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Mark Harry
Post Laureate
Reged: 09/05/05
Posts: 3121
Loc: Northeast
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(What you did was make "amber". Got any bugs in it?)
M.
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So many projects, so little time!
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