First (and last) time is use powder developer...

[Tom Pinchenzo]

So I’ve always used ilford ddx developer (liquid) but was trying out D-76. I added the powder to water and it started to dissolve but before long an impenetrable crust formed at the bottom of my cylinder. I eventually managed to break it up (poking it with a carving knife) but was left with equally solid blocks. I got impatient was poking them with the thermometer. Thermometer breaks... developer goes down the drain. Bah!

 

[Stegosaurus]

 

[excalibur2]

.....even adding the powder in slowly while stirring?

 

[ancient_mariner]

Don't dissolve bulk powders in a cylinder unless you want this to happen. There are techniques for getting solid chemicals into solution efficiently (part of my background is manufacturing bulk diagnostic reagents) that will help. Brian's approach is probably the easiest one at home - and let me add that you should do it in a wide-mouthed container like a jug - preferably using slightly warm water

Out of interest, was that a mercury thermometer?.

 

[Tom Pinchenzo]

.....even adding the powder in slowly while stirring?

All in one go. I thought it would be something like dissolving sugar or salt. I even thought while pouring ‘hmm, this might come out faster if I made the hole bigger’. I did try adding hot water but it didn’t do much.

@ancient_mariner no it wasn’t Mercury. I don’t think they still made mercury thermometers?- mainly for this very reason....

 

[excalibur2]

There must be a scientific reason why putting too much powder into water in one go forms a crust (well for some powders), as I made the same mistake not so long ago by putting too much caustic soda powder into water and ended up with a crust and lumps.

 

[Thmaga]

All in one go. I thought it would be something like dissolving sugar or salt. I even thought while pouring ‘hmm, this might come out faster if I made the hole bigger’. I did try adding hot water but it didn’t do much.

@ancient_mariner no it wasn’t Mercury. I don’t think they still made mercury thermometers?- mainly for this very reason....

I don't think they do, but there's a lot still around. My film dev kit has one.

 

[StephenM]

I don't know if mercury thermometers are still made; Paterson years ago made both spirit and mercury thermometers and sold the mercury ones as more accurate. I still have three (one to use, a spare and a spare spare). Breakage is the reason we were taught at school to never use a thermometer to stir anything. We had glass rods back in those days to stir with.

On dissolving bulk amounts. I know that flour does not actually dissolve in milk, but the principle is the same. If you start with the flour for a Yorkshire pudding in a bowl, adding all the milk at once will produce hard (or impossible) to remove lumps. It's the same principle in reverse. Do it gradually.

Still, on the bright side you've learned the lesson now.

 

[NickT]

Make 1 US gallon in a bucket at the right temperature and you won't have any trouble.

 

[Box Brownie]

Back in the day I sold many a heated (and non heated) magnetic stirrers for mixing lab sized volumes of liquids..................plus lots of PTFE coated stirrer magnets to avoid cross contamination and/or special cleaning requirements.

The range of places I called upon covered many industries, some in the infancy of developments i.e. the first ever UK plant for making CD's and University pilot plants where they were developing fibre optic cables.

But to the point, as mentioned above you need as wide a mouthed mixing container as you can use and stir the powder progressively into the liquid......only adding more as the bit already in it has dissolved.

 

[Peter B]

I use a demijohn as it's easy to hold onto for a good shake. You still have to add the powder a bit at a time though, but it's quicker than making your tea and far more satisfying.

 

[Asha]

Interesting thread as I will soon be mixing my recently acquired ID11 powder developer.

I know a neighbour with a milk churn ...... perhaps lug it with water and powder up a local mountainside, add contents at the summit and send rolling back to my home to arrive suitably mixed

 

[ancient_mariner]

There must be a scientific reason why putting too much powder into water in one go forms a crust

Some chemicals form rigid crystalline structures very rapidly when mixed with water, and if there's a large mass of chemical together then it will crystallise into a hard porous lump. For material to dissolve, molecules have to be stripped away from the surface, and where you have a large surface area - for example a finely divided powder - this can happen rapidly. However if the chem has formed a large crusty lump then the surface area is relatively small and it takes a very long time to dissolve.

Not everything behaves like this, and it's often faster to dissolve proteins, detergents and sugar in a relatively small volume of water where they can be mixed vigorously, rather than a large volume where they go round and round with little force to act on the boundary layers surrounding the gradually dissolving material.

If you want a good alternative to a stirring rod then buy a plastic whisk that will fit in the end of your drill and set-to with that (but wear safety glasses in case of splashing - seriously!).