Pickling with Oxalic acid

[rasorbackq]

  Noticed the last few times I used the acid to pickle the hide had brown spots on it   Last two were deer hides,  this last time its a bob cat that appears to have brown tan colored spots on the leather.     Pickle is maintained lower then 2  for pH and at 70 deg .  Could the powder be too old? its less then a year.
 Hide was fleshed on a beam  then salting and 48 hrs pickle is where I am now.
  With the last hides even after shaving and back in the pickle it never turned white  brown patches seemed to grow more places.

  Never noticed before I started to shave.

[muscle20]

       To me it looks like some sort of stains like maybe blood,bruises ? I do not look at the pickle process to turn the skin white, I refer it to be pickled through when the depth of the pickle has penetrated through the corium turning it from a raw state which is part tranlucent to a pickled state which would be a opaque . I have had methanoic acid loose its strength, but I have never experienced ethanedioic acid to, as you state go bad. Did you have to add more acid than normal to adjust the pH down?

[rasorbackq]

 Muscle 20  ...... I should have added acid on third day as it was at 3ph in the morning. I just raised to 4 and dropped in the Lutan F  spots are still visible after tanning.

[John C]

looks like bruises.

[cyclone]

Bruises....how did you re hydrate?

[rasorbackq]

 I salted for 2 days and then washed it washing machine  No  soap just cold water. I don't dry hard as I tan in house  Seems some say to dry hard then rehydrate  even for in house tanning  while other say not required.

[Bruce Rittel]

I used Oxalic Acid for pickling years ago and never had this staining reaction. I always kept it at a stable 1.5 pH throughout the pickling stage. The fact that you say it was at a 3.0 pH would indicate that something was wrong. That is extremely high for an Oxalic Acid pickle. Do you use the formula - 1 Oz. of Oxalic Acid, 1 Lb. of Salt and 1 Gl. of Water? If so, your pH should be around 1.5 pH!

A wild guess would be that your Oxalic Acid has been contaminated with something else, or check the pipes above where you pickle or tan. Sometimes moisture dripping from the pipes can cause strange results too!