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A discussion of PH

Discussion in 'Tanning' started by Rhino, Dec 22, 2009.

  1. Rhino

    Rhino Too many irons in the fire will put the fire out!

    Livingtrophy, Im hoping Glen Conely will jump in here, by Saturday. He probablly has some photos for us, on this topic?

    Cyclone, your actually helping me understand a few things! ;D Keep it up!
     
  2. craigjw

    craigjw http://www.back2lifetaxidermy.com

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    Craig. what EXACTLY do you put in your 8 gallon pickle, and EXACTLY how do you neutralise? Yes you can have too much salt.





    [/quote]

    I do 2 deer capes with 8 gallons, and neutralize with baking soda, usually soak for 30 minutes and check ph of skin when done

    When adding salt while adding acid, how much do I need to add, at what point is it too much?
     

  3. craigjw

    craigjw http://www.back2lifetaxidermy.com

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    Cyclone, you said to keep track of how much acid I add and start with that. I would guess that would make it start very low, is that OK?
     
  4. cyclone

    cyclone Posts: 400001

    If your pH is rising and you have to add more during the course of the pickling stage, That rise is due to to the acidic protons being neutralized whether by something within the hide or on the hide. If you start out with 10 oz of your acid at the beginning and add another 5 oz the next few days to bring it back down, Why not start out with 15 oz at the beginning?

    Different acids affect pH differently. I can add a truckload of formic acid (a weak acid) with the confidence that the pH will not drop much below 2. It is the nature of formic acid. I know that if I add 2 truckloads of formic, I might get the pH below 2 but I still have 2 truckloads of acid to neutralize.
    Only a certain number of the formic acid molecules will go to work while the others remain idle but at the ready...

    Use a acid like hydrochloric (a strong acid) and all of the available protons will go to work. Hydrochloric has no lazy protons. It will drop the pH like a rock...


    Notice (a weak acid) and (a strong acid) in parens... To a chemist these notations have special meaning. Strong acids, by definition, donate all of their acidic protons when in solution.. Weak acids only donate so many acidic protons the others are held tight to the acidic molecule..



    Chew on that awhile, I have some Christmas cookies to eat...

    MERRY CHRISTMAS ALL...

    cyclone..
     
  5. craigjw

    craigjw http://www.back2lifetaxidermy.com

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    Whats the best acid to use, strong or weak. I have used citric and safety acid. I use only safety acid now, it seems like a weak acid and easier to neurtalize. So is it good to be easy to neutralize?
     
  6. msc

    msc New Member

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    Tn
    I was also wondering of ill effects of neutralizing for too long
    if left in too long will the ph get high enough to cause any problems
    I just assumed this was the key to the time frames always given in the instructions
     
  7. Rhino

    Rhino Too many irons in the fire will put the fire out!

    Thanks for this post Cyclone! You have got me studying like hell now!

    http://www.chemtutor.com/acid.htm#pkabx
     
  8. cyclone

    cyclone Posts: 400001

    The best acid to use is the one that you have the most success with. I like formic. I have a good track record with it. I have also tried a mix of formic and safety with great results. I've never used citric.

    You have to watch any pickle mixture when you first add your capes. Test the pH often and adjust as needed.

    Yes, you can over-neutralize. Over-neutralize the pickle hide and your pH will be too high for the tanning agents to properly affix to the collagen.


    Over-neutralize the tanned hide and you can very well break many of those crosslink bonds that the tan created. It can cause hair loss, epidermis loss and easily torn hides...

    The good news for us home tanners is sodium bicarbonate, aka baking soda, creates a very nice buffered neutralizing system. It's not going to go much above a pH or 8 or 9 no matter how much you add.

    The acid in a hide is not instantly neutralized. The time it takes is dependant upon the type and thickness of the hide. Rabbit theoretically should neutralize more quickly than a deer unless you have your deer as thin as that rabbit.

    You folks that haven't tried it yet have really got to get your gloved hands in that neutralizing bath and squeeze the hide...

    Feel the bubbles... ;)
     
  9. paul e

    paul e New Member

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    great post guys
    now i know why every now and then
    you get a different feeling skin
    great food for thought

    most of us are scared to over do the baking soda

    your saying not to go crazy with it but using more will probably help if you monitor the pH of the solution in the skin while neutralizing
     
  10. Monte

    Monte Missouri fur-Limited hair-tanning

    Question, how do you all keep from precipatating out the tanning agent when you neautralize the pickle to a pH above the precipatation point of the tanning agent?
    For example; alum 4.1
    syntan 4 to 5
    lutan F 4.1
    lutan cr 4 to 5
    liqua-tan 4 to 5


    Just curious.
     
  11. cyclone

    cyclone Posts: 400001

    Monte,

    I'm removing my hide from the pickle and putting it into a bucket of fresh water. I then add the bicarb in excess and monitor the pH of the skin.. When the skin gets to about a pH of 5, I pull it, rinse with clean water, spin dry and apply the Liqua Tan..

    I would assume that you (tanneries) adjust the pH of entire batches. You have to be more exact with your final pH..


    See the above post:

     
  12. Monte

    Monte Missouri fur-Limited hair-tanning

    Cyclone, I can see how your procedure would be a lot closer.
    I neutralize after the tanning agent has been run for an hour and a half to 3 days depending on what I am tanning to the exact pH. Then the whole batch is rinsed for 20 min. at a higher temp.
    I have soaked our dry tan for over 2 weeks in plain water with no swelling and no hair loss. Controlling pH is vital for max. fixation.
    Have you ever used liquid indicators to check how consistant the pH is through the thickness of the hide. I understand this may not be necessary with home bucket tanning if you get the results you want.

    When I tanned buckskin if we were off 1/10 of a point on the pH when dying the color would be different and not match from batch to batch.

    On the hair-on skins for taxidermist we would hold 2/10 of one point.

    Most home tanners should follow your method.