Wednesday, March 23, 2011

Testing, testing testing....

Since we have spent so much time, discussing volumetric measurements, I think its time to round this up.

By nature I measure everything in the metric system, I grew up in a 100% metric society, I was formally trained as a chem. engineer using that system.

I've been reloading ammunition for close to 30 years, however, and noticed early on that they used another system in USA, this caught my interest. I have tried and uses volumetric measurements in reloading ammunition, both for high-powered rifles and pistols for years and years, and it is every bit as reliable and safe as using weights.....

So when I came across people on the net that used volumetric measures for mixing developers, I shaked my hhead at first.  Becuase, contrary to home reloading, there exist no standard measures. For powder a company named Lee Prescision, among others have produced and sold measurement kits for years, and done research into
powder specific weights, and updatetd those over the years, to make a reliable system.

Nothing like that exists in photo chemicals.

Still a LOT of people uses this system, because they don't know better, don't know the metric system, and because they have some measuring utensils in the house.

So I set about trying to dechipher some of the recipes, and to try and see if they can be translated......

I have published in this blog a reliable sytem on how to do this, based on Reinholds recipes on his Blogspot blog.

I cannot stress enough : all my recipes are in fact Reinholds CC-M or CC-H recipe, adapted to specific use in practical situations! 
(CC-M and CC-H is one and the same recipe, the difference being ca 1 gram KBr per litre to control fog levels in the CC-H recipe, since I have ample supplies of KBr, I use CC-H most of the time...)

I have a prescise and \reliable weight, so I have checked my volumetric measurements over and over again.

In a little debate with Reinhold he raised the point of specific weight, even if I think that is moot, I have given it a little thought.

The theory is simple measure out with the meaure, weigh it, and divide by volume, THAT is specific weight.  This I have done and reported and reiterated here in this blog.

Yesterday it dawned on me: I took it for granted that the 5ml-marked teaspoon measure was reliable, that it really contained 5ml.  But I have never tested that!

OK. Must do that.

Also, since there are many measures around the world, acn anything be said about OTHER measures sold?  Definitely, I went on a shopping spree and found two kits of measures here locally.

Then I tested all my 3 kits, to see if there are any differences.

This is my standy Aluminum kit, I have a hunch its a french kit, I think my wife got it from France via the net.....

I concentrated on the teaspoon and the tablepoon measure, mared 5ml and 15ml respectively. Since 1ml is equivalent to 1cc, this has been my base for calculating specific weight also.

But what if 5ml is not 5ml, what if the measure is a bit off?

OK a test is simple and practical :
I set up a weight and a reliable, old german Schottky-glass measuring cylinder.

Then I used clean water, and measured out 20 meaures from the 1 teaspoon measure (5ml), noted the volume and then weighed the resulting water. After that I did the same with the tablespoon measure (15ml).

I rounded up the test with my other two, brand new measurement kits:

These are the plastic measures, they cost NOTHING, since the store was selling them off and anyone that want one, just mail me - I got 3 and can get more for a song!!
The store in question was -Nille a cheap chinese goods chain over here...

I concentrated on the teaspoon and the tablespoon, this kit is made in Sweden and marked in swedish : 5ml Tesked and 15ml Matsked, number 2 nad 4 from the right respectively.

These seem to be sooper quality chinese brand measures, made from stainless steel, thhe store was Jernia, which is a kitchenware and tools chain over here and these where expensive...

Again I concentrated on the teaspoon marked 1 Tsp 5ml and the tablespoon marked 1 Tbsp 15ml, those are number 2 and 4 from the right respectively.


Aluminium measures (France) 
1 Tsp (5ml)      :    4,84 ml    weight of water = 4,76 gram
1 Tbsp (15ml)  :    15,50ml   weight of water = 15,23 gram

Plastic measures  (Sweden)   
1 Tsp (5ml)      :    4,78 ml    weight of water = 4,69 gram
1 Tbsp (15ml)  :    15.25ml   weight of water = 14,97 gram

Steel measures (China)   
1 Tsp (5ml)      :    4,85 ml    weight of water = 4,80 gram
1 Tbsp (15ml)  :    14.33ml   weight of water = 14,17 gram


Deviation from marked volumes :
My 3 kits did show marked deviation from what is marked:

Teaspoon : Average volume : 4,82ml,  deviation 3,5%
Tablespoon : Average volume : 15.03ml, deviation 0,1%


This does not undermine the volumetric measures already published here.
It does however have a bearing on the specific weight published.  Specific weights measured and published needs to be adjusted for actual volume in the measuring device, I have now claibrated mine, and here published how to do that for others.

For practical use, this is of moot interest. Just go about, use any measure, and wegh out how many grams YOUR mesaure gives, and use that weight as a base.

For me I'm still perfectly happy using my measures, measuring out 3-2-7 measures (tsp) to get one (small) tankfull of developer for my JOBO or Paterson tanks, to develop 1 35mm film with 11 oz of developer to be sure I cover all the film in both tanks, or measuring out 5 - 3 - 13 measures (tsp) of developer to develop 1 or even 2 films of 120 on the same spool with 18 oz of developer.

Volumetric measurements are quick, reliable and very practical, once you do your homework!

And I will stress once more, this is the same recipe as published by Reinhold, Coffenol CC-H 


Finally a deviation of 3,5% is well within what can be expected with weights, simple kitchen weight have far bigger deviation, even small chemistry-kit weights might have more, but simple, gravity-driven weights have usually excellent REPEATABILITY.

Electronic weights on the other hand are (sometimes) far worse.  Often their claimed acuuracy is far from the advertized, and repeatability sometimes not reliable at all, and worst they sometimes give totally false reading without warning. Therefore prudent use of electronic weights are in place, the upside usually is that when they fail they fail spectacularly, so it will be obvious to everyone.

Volumetric  measures in comparison is utterly simple to use, the only danger being counting out the wrong number of measures!

Good luck, whatever path you choose.

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