[QUOTE=Jed Freudenthal;620605]
Quote Originally Posted by Merlin View Post
(omdat het draadje off-topic werd, heb ik hier de discussie voortgezet als nieuwe draad.)

Verder heeft de 'gewone' D76 een meer merkbare densiteit bij fog (is daar een nederlandse vertaling voor, anders dan mist?).

De D 76 heeft geen remmer omdat de hoeveelheid borax zo laag. Daardoor is de sluier laag en hoeft er niet geremd worden. Ik herinner me nog een artikel van Crabtree ( zeker 50 jaar geleden), waarbij de borax verhoogd werd ( en de ontwikkeltfijd verlaagd). Hierbij zal het hydrochinon probleem ook omzeild zijn. Dus Crabtree zal, zonder het te merken, de iinconsistentie hebben omzeild, omdat de pH hoger werd. Crabtree was Haist dus een slag voor.

Jed
Hier wat knip en plak werk uit mijn "archief".., citaten van Richard Knoppow:

(voor een deel al genoemd denk ik)

Mvgr,

Cor

Ps ik had altijd begrepen dat kodaks D76 een uitstekende ontwikkelaar is, en als een "benchmark" beschouwd wordt. in het verleden heb ik op kleinbeeld prima resultaten behaald. Ben overgegaan op Xtol om iets meer snelheid te behalen (1/3 stop in de praktijk), de korrel zou kleiner zijn (zou ik grondig moeten vergelijken, weet ik niet), en het is wat milieu vriendelijker (ascorbinezuur zuur en phenidone als ontwikkel stoffen)
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>

> Te difference between buffered and unbuffered d76 is only
> a little bit of boric acid, isn't it? (my books are still
> in Wilma-proof boxes). If so, isn't it possible to make
> ID11 into a buffered D76 by adding a pinch of boric acid
> on mixing?
>
> Boric acid is available even from grocery stores for those
> who don't stock raw chemicals.
>
> Bert


The original D-76 formula and Ilford's published formula
for ID-11 are:

Water (at 125F or 52C) 750.0 ml
Metol 2.0 grams
Sodium Sulfite, dessicated 100.0 grams
Hydroquinone 5.0 grams
Borax, granulated 2.0 grams
Water to make 1.0 liter


The formula for D-76d, the buffered variety is:

Water (at 125F or 52C) 750.0 ml
Metol 2.0 grams
Sodium Sulfite, dessicated 100.0 grams
Hydroquinone 5.0 grams
Borax, granulated 8.0 grams
Boric acid, crystalline 8.0 grams
Water to make 1.0 liter

With this amount of Borax and Boric acid the activity of the
buffered developer is the same as that of freshly made D-76.
The activity stays stable over long periods of time.
The activity of the buffered developer can be varied by
changing the ratio of the Borax to Boric acid, the total of
the two remaining the same.
It is probable that the packaged forms of both D-76 and
ID-11 are slightly different. Probably both contain
sequestering agents and possibly other stuff that is present
in too small an amount to show up on the MSDS.

In the USA 20 Mule Team Borax is chemically pure enough
for photographic use according to its manufacturer. However,
be careful not to get "Borax Cleaner" which contains soap
and other ingredients. Boric Acid is sold in many
drugstores. People used to soak their feet in it.

---
Richard Knoppow

> BTW, Richard, it looks like you are correct about the
source of D76H. A&S
> say that Haist developed the formula because he wanted to
avoid the
> hydroquinone (therefore also Borax). Apparently its
activity is altered by
> any rise in pH that might occur over the lifetime of the
mix. That seems to
> be the reason A&T say they strongly recommend D76H for
home brewing. I'm
> only just trying this for the first time, and probably
will only use it for
> sheets of Maco 820ir; so I don't expect my small batches
to involve ageing
> or pH changes. But D76H does seem more straightforward.
>
> Below are the variants, from A&T (p.43).
>
> Their Kodak D76:
> 2g Metol
> 100g Sod. sulfite
> 5g hydroquinone
> 2g borax decadyrate
>
> Their D76D:
> 2g Metol
> 100g Sod. sulfite
> 5g hydroquinone
> 8g borax decadyrate
> 8g boric acid
>
> Their D76H:
> 2.5g Metol
> 100g sod. sulfite
> 2g borax decahydrate
>
> Mike Healy
>
Heigh-Ho, I KNEW that. What has happened to my brain? My
memory is not just a sieve, its a collander.

Anyway, Haist may have recomded this but someting very
like it was shown as one of over thirty variations of D-76
given in a long paper on it by Carlton and Crabtree of Kodak
Labs. This is the paper which announced buffered D-76.
Although the authors had not figured out that the rise in pH
was due to a reaction between the Hydroquinone and sulfite
they did find that using a buffer of borax and boric acid
would stabilize the pH and thus photographic activity.
Carlton and Crabtree experimented with formulas without
Hydroquinone or with Hydroquinone but no Metol. They found
that at the low pH of D-76 the Hydroquinone was virtually
inactive as a developing agent. When made up with Metol the
developer was about as active as the complete formula. The
disadvantage was the capacity of the formula.
In the mid 1940's Kodak Labs announced formulas D-23 and
D-25. I am sorry but I don't remember the authors but I will
find the reference and post it later. Both of these are
developers with Metol as the sole developing agent. D-24 is
Metol and Sulfite and has characteristics similar to D-76.
D-25 is the same formula but buffered to neutral pH with
sodium bisulfite. This buffering reduces the activity of the
developer to the point where the solvent action of the
sulfite delivers extremely fine grain results. Kodak stated
that the grain was as fine as gotten by the use of a Para
phenylenediamine developer without the toxicity and with
better tonal characteristics.
D-23 is about as simple as you can get:
Kodak D-23
Water (at 125F) 750.0 ml
Metol 7.5 grams
Sodium Sulfite, dessicated 100.0 grams
Water to make 1.0 liter

Times are about the same as fresh D-76

D-25 is:

Kodak D-25 Extra Fine Grain Developer
Water (at 125F) 750.0 ml
Metol 7.5 grams
Sodium Sulfite, dessicated 100.0 grams
Sodium Bisulfite 15.0 grams
Water to make 1.0 liter

By adding some Borax to a developer like D-23 its activity
can be raised somewhat.
One reason for the larger amount of Metol in these two
formulas is to extend their capacity.
I have no idea of what the advantage of adding the borax
is since the simpler D-23 formula is satisfactory.
In the Carlton and Crabtree paper a comparison of the
activity of the original D-76 and the buffered formula is
made for a period of two months. The standard formula
increases in activity to the extent that equal gamma is
gotten in not much over half the time as in freshly mixed
developer. The buffered formula showed no increase in
activity within the experimental error.

1, "Some Properties of Fine-Grain Developers for Motion
Picture Film" H.C.Carlton and J.I.Crabtree (Kodak Research
Laboratories), _Transactions of the Society of Motion
Picture Engineers_ Vol. XIII, NO. 38, 1929 p.406
Also see: "Borax Developer Characteristics" H.W.Moyse and
D.R.White (DuPont Film Manufacturing Co.) ibid, p.445


---
Richard Knoppow