I don't see the point of worrying about a triple beam balance. Worry about the weights. You might worry about the slider, but the scale it slides on surely hasn't changed. How much of the slider could have been worn off over the years? If you can set the tare adjustment so that the balance balances with the slider at 0, go ahead and weigh a coin, but you will probably find it still weighs the same as it did when the balance was new. I suppose there could be some wear or corrosion of the knife edge, but you would see that as hysteresis.
Mke sure the balance is close to level when you use it. You can change the balance point by moving the tare weight or by raising one end or the other of the base. I leave it to you to discover which is better.
If you want 0.01 gram accuracy, you don't want a triple beam balance.
I use a scale that is digital and measures to about 1/100 of an ounce. These scales cost about 20 bucks. The actual measurement it reads is in tenths of a gram. If I tear off a piece of paper the size of my thumb nail it will register. Thats probably the easy way to weigh chems.
Penny Standard weight 2.5 grams
Nickel Standard weight 5.0 grams
Dime Standard weight 2.268 grams
Quarter Standard weight 5.670 grams
I can tell you from personal experience that some pennies come out at 2.4, some nickels come out at 4.9. It varies a bit but that variation won't kill you. Phenidone I believe is what you want to meaure correctly. Otherwise there is room for error IMHO.
i used a nickel. and then i dove in. i had to weigh out 750g. i did not think it was accurate at that weight so i reweighed it in 200g increments...it came out good.
i developed my first set of negs last night.....well.....it worked! i guess i was close enough.
so the phenidone is the most crucial huh? my recipe only called or 2g of phenidone amazing that a small amount will through it all off.
Those chemicals that will keep well in solution can be measured out into 10% (or higher or lower) solutions. Then when you need only 0.1g of something you can go back to your solution and extract the appropriate volume to contain 0.1g of whatever. Keep in mind that if you do use solutions to manage your small quantities, the total volume of water (or whatever fluid you have selected) in your formula is affected by the addition of your percentage solution.
In other words, you are adding not only the 0.1g of X but also perhaps 100ml of water so subtract that 100ml of water from what is called for in the recipe.
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My understanding is that quantities of phenidone need to be precise in absolute terms simply because the quantities are so small. For instance, if a formula calls for 0.5g of phenidone, an error of 0.1g represents 20% of the target amount, whereas an error of 0.1g in 5g of metol would be just 2% error. As rwyoung suggests, mixing a stock solution can help with this if your scale isn't precise enough. For phenidone, propylene glycol is a good option for a solvent; phenidone reportedly keeps quite well in propylene glycol.
Also, consistency is more important in most photographic processes than absolute accuracy. Two persons may get slightly different results from what is ostensibly the same process. If you were to use different sized pebbles as your standard weights, you couldn't tell others exactly how to duplicate your results, but you could duplicate them for yourself with each new batch.
Originally Posted by Phillip P. Dimor
The most precise measurement of weight is by substitution. If you want a penny's worth of phenidone, put a penny in a container on the pan and do whatever is necessary with the sliders to balance it. Remove the penny and add phenidone to the same container until balance is restored. Put that penny away for safekeeping and use it every time you need a penny's worth of something (other than thoughts). Now you need have no concern for the accuracy of the weights. You can use your own set of pebbles or other found objects to make a truly personal developer. Nobody can steal your recipe, but you can make it the same every time.
Anybody who says I'm not a bit "off" is a bit "off".
Seven hundred and fifty grams. I'd have used
Originally Posted by eddie gunks
a quarter. That many grams of something plus
two grams of phenidone. Some formula! Dan