Neutrino This time I’ve got a quick maths question for you regarding dilutions. It occurred to me recently when I was comparing single-use developers in terms of yield and price. Not that I’d buy a particular developer (solely) on the basis of price, but I did find it interesting. € A developer with a standard dilution of 1+4 in a 1-litre bottle has the same yield as a developer with a standard dilution of 1+9 in a 1/2-litre bottle. Consequently, if for whatever reason you wanted to dilute a developer with a 1+4 ratio to twice its strength, you would need to add a further 5 parts of water. The double dilution of 1+4 would therefore be 1+9 and not 1+8, as one might initially assume. Am I correct in this? €
grommi You’re absolutely right, Neutrino. It’s a recurring issue with Rodinal in particular, and I recently made a terrible mistake with it elsewhere too. 1 + 50 = 1 : 51, but that’s hardly relevant; however, with Xtol, for example, 1 + 1 = 1 : 2, which is of considerable importance. I find the ratio much clearer than the addition. 1:10 is exactly double the dilution of 1:5. This corresponds to 1+9 or 1+4. Actually quite simple … actually …
Neutrino It’s a bit late, but thank you very much for your explanation! So it really is just as I thought.
Commander8x Just a quick note from me: the specification "dilution 1+4" is read as "1 part concentrate + 4 parts water". This means you have a total of 5 parts by volume. For a 500 ml working solution, that works out as 100 ml concentrate + 4 parts water. ? The specification “dilution 1:5” is equivalent in meaning. Read this as “1 part concentrate to 5 parts total volume”; this is the same as 1+4. ? That’s right. If you keep making the same mistake and still get consistently good results, then everything’s fine, isn’t it? ? :spudnikwaving: ? And what Edith wanted to add: the greater the dilution, the less significant the error becomes.
MirkoBoeddecker +25. Strictly speaking, shouldn’t it be 1+51 then? It should be 1+24 and 1+49 (which is essentially the same), but with such high dilutions, the ‘neat’ notation 1+25 and 1+50 is used.
