Microwaving Potassium Oxalate

[Jeremy]

I am wanting a warmer tone to my palladium prints and I remember that heating the potassium oxalate will accomplish this. At this time I can't use a heating bath so I was wondering if anyone has microwaved their potassium oxalate to good effect.

 

[Jorge]

I am wanting a warmer tone to my palladium prints and I remember that heating the potassium oxalate will accomplish this. At this time I can't use a heating bath so I was wondering if anyone has microwaved their potassium oxalate to good effect.

Sure you can, but I dont think heating PO in the same MW oven that you heat your food in is a good idea. PO is not very toxic, but at high concentrations it can be a risk.
I would say heat it covered in small increments, you dont need to heat it too much, 90, 100 ºF is good enough.

 

[Jeremy]

Sure you can, but I dont think heating PO in the same MW oven that you heat your food in is a good idea. PO is not very toxic, but at high concentrations it can be a risk.
I would say heat it covered in small increments, you dont need to heat it too much, 90, 100 ºF is good enough.

I did thinks about that We have an extra microwave out in the garage that I could steal for this express purpose. I may just try and heat up a jug of water in the microwave, pour this in an 11x14 tray into which I could place an 8x10 tray to which the developer could be added. Or I could take a gallon jug and cut the top off of it and put my jug of pot ox into that and fill the cut jug with hot water so as to heat up the pot ox before pouring into the tray (I sometime work with 11x14 trays and don't have room anymore for a 16x20 tray to place the 11x14 into).

Thinking...thinking...

 

[Michael Mutmansky]

Jeremy,

I occasionally use a microwave to quickly heat up PO. You may want to invest in a large Pyrex mixing bowl to use for the purpose. Some of them come with a rubber top. This is ideal because it reduces the vapors, and holds heat in. It pours faster than a bottle, too.

Make sure it isn't too large for your microwave before you buy it.


---Michael

 

[Silverpixels5]

I know Clay microwaves his K Oxalate. He actually has the time narrowed down to give him the temperature he needs for the color he wants. A pyrex measuring cup should work fine.

 

[clay]

Yeah, I buy the pyrex 8 cup (2 liter) glass measuring cups with the plastic lid on them. It is important to keep it covered in the microwave to minimize any splashing and also keep the evaporative water loss to a minimum. Even with that, you may have to add a little distilled water occasionally if you start noticing crystals of k-ox on the bottom of the storage container. In my microwave, 1.5 liters of k-ox will go from room temperature to 140 degrees in six minutes. I then zap it with 1-1/2 minute bursts after each development to keep the temperature at about that level. For really warm prints, try it at 145 to 155 degrees. You can get some good results with even hotter temps, but you start flirting with the possibility of breaking down the sizing of the paper and getting some strange unwanted results. Some papers seem more robust than others. I find that platinotype (yuchhh!) and stonehenge start to break down at 150 degrees or so. Platine and Cot seem to be able to stand hotter temperatures. Whatman's is pretty robust as well. As always, YMMV.

 

[Joe Lipka]

I go in the opposite direction. I made a hot water bath from a styrofoam "cooler" and an aquarium heater. I heat up about two liters of water in the MW then put it in the "cooler" with the aquarium heater and the glass jug of developer. Wait a bit and the developer warms up to 100-110 degrees F. The only hassle is pouring the developer in and out of the developer tray. We must suffer for art.....

The simple styrofoam cooler. It keeps hot stuff hot. It keeps cold stuff cold. How does it know? :confused:

 

[sanking]

For really warm prints, try it at 145 to 155 degrees. You can get some good results with even hotter temps, but you start flirting with the possibility of breaking down the sizing of the paper and getting some strange unwanted results. Some papers seem more robust than others. I find that platinotype (yuchhh!) and stonehenge start to break down at 150 degrees or so. Platine and Cot seem to be able to stand hotter temperatures. Whatman's is pretty robust as well. As always, YMMV.

I am confused as to exactly what you are doing? Are you heating the ferric oxalte to mix it from powder, or heating it before mixing it with the sodium chloropalladite, or heating it after combining withe the sodium chloropalladite?

Sandy

 

[wm blunt]

Sandy,
They are talking about dev. not ferric oxalate.

 

[sanking]

Sandy,
They are talking about dev. not ferric oxalate.

Thanks. That seems very clear on second reading!!

Sandy

 

[titrisol]

It should work, k-oxalate solutions have excellent dielectric properties so it should heat up faster than plain water.
Try 1/2 the time you'd use with water as a start point

 

[Michael Mutmansky]

There's another reason to keep a lid on the PO at all times. I've been told that it is quite corrosive, so you will probably want to avoid getting any into the air, where it can start to work on the metal in your darkroom.

I don't know if this is true, but I figure it's better to take a few precautions.

---Michael

 

[titrisol]

According to the MSDS the powder seems to be a lot more toxicn tahn solutions of it.
It is not volatile, but the powder can be fine, a granular type would be better to minimize those risks:

J.T. Baker SAF-T-DATA(tm) Ratings (Provided here for your convenience)
-----------------------------------------------------------------------------------------------------------
Health Rating: 3 - Severe (Poison)
Flammability Rating: 0 - None
Reactivity Rating: 1 - Slight
Contact Rating: 3 - Severe (Corrosive)
Lab Protective Equip: GOGGLES; LAB COAT; PROPER GLOVES
Storage Color Code: White (Corrosive)
-----------------------------------------------------------------------------------------------------------

Potential Health Effects
----------------------------------

Inhalation:
Inhalation of dust is corrosive to mucous membranes. Oxalates can be absorbed through the lungs. Symptoms of poisoning include nervousness, cramps, central nervous system depression.
Ingestion:
Mean lethal dose for oxalates in adults is estimated at 15-30 grams with death within a few hours or even minutes. Corrosive action on the mucosa and severe gastrointestitis can occur with pain, vomiting, etc. Sharp reduction of serum calcium can cause disfunction of the brain. Calcium oxalate may be deposited in the kidneys.
Skin Contact:
Corrosive. Symptoms of redness, pain, and severe burn can occur.
Eye Contact:
Corrosive. Contact can cause blurred vision, redness, pain and severe tissue burns. Prolonged contact may cause eye damage.
Chronic Exposure:
Circulatory failure or nervous system irregularities may follow prolonged calcium metabolism disturbances due to oxalation.
Aggravation of Pre-existing Conditions:
Persons with pre-existing skin disorders or eye problems, or impaired liver, kidney or respiratory function may be more susceptible to the effects of the substance.


I wouldn't heat with the lid on, but in a half full container, there's less risk this way because when you microwave with lid on vapours are promoted.

 

[Joe Symchyshyn]

I like to use one of those coffemug warmers. It's like a little hotplate that holds a mug sized container. I just sit the bottle on it and leave it there warming up and staying at the same temperature for the session.

Not sure what temperature it got to exactly, but was warm.

joe

 

[titrisol]

I decided to test k-oxalate in the MW oven for myself.
First I measured dielectric properties of 0.1, 0.5, 1, 2, 5 and 10% solutions

Increasing the concnetration of k-ox increases the "loss factor". Thus, heating is more efficient at higher concentrations.
A 1% solution will heat 3 times faster than water, and a 10% solution about 5 times faster.

In an old crappy box I have here (it's almost shot), I was able to heat 1 cup (250 ml) of 1% solution from room temp (about 25C) to 80C in about 1:00. In a household MW box, it should take about 20 sec

So beware of the speed of heating, and start with short times. Use a half empty container to heat, it'll avoid spills.