Doesn't heat degrade Ascorbic Acid as well at a temperature as high as 200 F? According to scientific literature it does and IIRC @albada worked at a much lower temperature for his long lasting Mocon concentrate.
For the Ascorbic Acid dry solid, it decomposes at 191 °C (https://doi.org/10.1016/j.jpba.2013.01.018). I don't know the decomposition temperature in TEA (might be much lower, as in water), it seems that Gainer initially reported that using 110 to 120 °C (250 F!) is also safe. But I prefer mixing at lower temperatures, as mentioned earlier, I don't like thick, hot liquids that don't emit steam, it's very likely for me to misunderstand that they are not so hot.
Your experience is valuable, while methods can vary based on the situation. I have an heated magnetic auto-stirrer, so there's no need for high temperatures to speed up dissolution. I simply add everything to TEA and stir at 60-70°C overnight or for a few hours. (Not a suggestion, just a casual chat.)
There are various approaches to achieve the same target if we understand what the goal is, such as using a microwave to heat up TEA to 120°C(manual stirring) or a boiling water bathauto/hot plate to reach 80-90°C(more manual stirring). Each method has its pros and cons. Personally, I prefer avoiding the risk of spilling hot liquid out, though many have the skills to handle it safely and hope to complete the mixing quickly, either way is fine..
Doesn't heat degrade Ascorbic Acid as well at a temperature as high as 200 F?
There are works that report substantial degradation of Ascorbic Acid in food when cooked at temperature of 80 C.
Decomposition no doubt requires higher temperature, but Ascorbic Acid starts degrading at modestly high temperatures. There are works that report substantial degradation of Ascorbic Acid in food when cooked at temperature of 80 C. Now, Gainer might have used sufficiently more Ascorbic Acid in his formulation that off-set the loss due to heat degradation. But I am not aware of any tests that he did to compare the activity of PC-TEA developer made from his concentrate with that made by dissolving the ingredients directly in water at the prescribed dilutions. I remain skeptical of any developer concentrate involving Ascorbic Acid and high temperature.
Gainer conducted experiments on Vitamin C aqueous solution developers before PCTEA (such as, https://web.archive.org/web/20011024073823/http://unblinkingeye.com/Articles/VitC/vitc.html), using ~2g/L concentration
If I have interpreted what you have said correctly and I happen to be someone who craves certainty then it sounds better not to add a pinch of sulfite
You're right. 1 l working solution of PC-TEA at dilution 1:50 contains developing agents in the same ballpark as Gainer's Vitamin C developers. However, the former is supposedly equivalent in strength to D-76 1+1 whereas the latter is equivalent to D-76 stock. So their activity is not quite the same despite similar amounts of developing agents. This could partly be due to the use of TEA in PC-TEA and partly due to loss of potency resulting from high temperature mixing. Without a proper test that compares PC-TEA working solution made from the concentrate with that made by dissolving the ingredients of PC-TEA directly in water at 1:50 dilution, we can't be sure.
Yeah. I also use a heated magnetic auto-stirrer. I was surprised at how much ascorbic acid you need to add, and how much it just doesn't want to dissolve. It was like an iceberg of ascorbic acid floating on the TEA. I kept increasing the temperature. I think I hit 90°C before it all dissolved. That thing looked like it could cause a serious burn. I'm glad I didn't have to stir 120°C TEA by hand.
The color change indicates oxidation (oxidation products of p-aminophenol derivative developers are red to brown in color, that's why old Rodinal looks like Coca-Cola). Preventing it shows that the oxidation has been avoided. I don't know what's confusing about that.
Thanks Donald So, just so I can be clear, you do support and use the " pinch of sulfite" first when mixing D23?
pentaxuser
Let me guess what happened. My ascorbic acid forms large crystals that settle at the bottom, while yours might be a loose, airy powder that floats on the surface with a larger volume. It might be helpful to moisten the ascorbic acid powder with a bit of ethanol or isopropanol before adding TEA.
pills meant for human consumption probably have a coating and/or a binding agent and who knows how that's going to affect my PC-TEA.
I do.
On balance it sounds as if sticking to the pinch of sulfite prior to the addition of metol is worthwhile
At the least, it's harmless.
Ascorbic acid in TEA is a developer (not a very good one) all by itself.I once crushed 2 acetaminophen tablets, and added them to TEA, with some ascorbic acid; I then let it sit for a week. Diluted with water, it darkend some film leader; I never did any real testing though, I was just curios if TEA was basic enough to convert it; it seams to be.
I once crushed 2 acetaminophen tablets, and added them to TEA, with some ascorbic acid; I then let it sit for a week. Diluted with water, it darkend some film leader; I never did any real testing though, I was just curios if TEA was basic enough to convert it; it seams to be.
More likely you confirmed that n-acetyl p-aminophenol is a developing agent in itself (as are most p-aminophenol derivatives). The TEA is alkaline enough to activate most developing agents, but IMO p-aminophenol is a better developing agent than acetaminophen. It takes a pH of about 11 (IIRC) to cleave the acetyl group off the paracetamol and make it into p-aminophenol (conveniently, Rodinal uses sodium hydroxide or potassium hydroxide as its accelerator).
Most presenters mention the pinch as being important to prevent oxidisation of the metol but your comment relegates the importance to that which Ilford rates the necessity of a pre-wash
So, is there no basis for the "pinch"" If there isn't then the make-up of D23 is even simpler as it then becomes "pour in all the metol then all the sulfite and stir
pentaxuser
There are a couple of other ways to "skin the cat". You can use distilled water, which is usually "flat" because it sat long enough to give up most of its oxygen. Or you can boil a gallon of water for at least five minutes and then let it cool a bit and then use it, boiling drives off both oxygen and any other gases and may also cause a substantial amount of mineral solids to either precipitate or coat the inside of your pan.
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