B&W Reversal Bleach — Hydrogen Peroxide/EDTA/Citric Acid

[artyfarty]

I have pure EDTA here and that's what Kentanghk and I did all the testing with. The amounts for the sodium salts were contributed here by @Anon Ymous . According to this link: https://longkey.com/blog/edta-2na-vs-edta-4na-key-differences/ it looks like the 4na salt has a lot higher pH and that probably should require a fair bit more citric acid to offset it. If it turns out you need a lot more, I'd be happy to update the blog post for this case! I think you're going to need to be able to measure the pH yourself (as you said). If the strips don't work out, the fairly cheap pH meters from Amazon have worked fine for me. If you overshoot the pH and get it a lot too low, you get little to no bleaching as well. It's important to be about right. Hopefully you can measure it with the new strips. Please let us know what you end up with. Good luck

Thanks, i'll try it!
It's hard to buy pure EDTA without actually getting poorly labeled EDTA-4Na. I've seen some EDTA-2Na options though.

 

[Raghu Kuvempunagar]

Check your Peroxide. It needs to be fresh to be effective as a bleach at as low a concentration as 3%. It deteriorates in storage over time.

 

[artyfarty]

Check your Peroxide. It needs to be fresh to be effective as a bleach at as low a concentration as 3%. It deteriorates in storage over time.

Thanks, i'll try testing it. Since it was propely packed etc i wasn't expecting any damage. BTW i can buy 30%, 40% or even 50% peroxide here, if it makes things simpler (it certainly would be cheaper).

 

[relistan]

Thanks, i'll try testing it. Since it was propely packed etc i wasn't expecting any damage. BTW i can buy 30%, 40% or even 50% peroxide here, if it makes things simpler (it certainly would be cheaper

If you are comfortable handling the more hazardous peroxide you could dilute it yourself. But please do read about 30% peroxide before taking that route.

 

[Raghu Kuvempunagar]

The advantage of higher strength Peroxide is that you can dilute it to not only 3% but also to a higher percentage (say 5% or 10%) if that helps the bleach work more effectively. However, as Karl rightly cautioned, you need to be more careful when handling and storing stronger Peroxide solutions.

 

[relistan]

This bleach is a very effective bleach at 3% peroxide at room temperature. So you won’t need higher concentrations. That was one of the criteria we set. But, if you are doing further experimentation on your own it could be helpful as Raghu says. However, peroxide is quite a strong oxidizer and even less than 3% would probably work if you have the time and inclination to further refine it. When we got to where it worked well repeatably, we stopped.

 

[artyfarty]

This bleach is a very effective bleach at 3% peroxide at room temperature. So you won’t need higher concentrations. That was one of the criteria we set. But, if you are doing further experimentation on your own it could be helpful. However, peroxide is quite a strong oxidizer and even less than 3% would probably work if you have the time and inclination to further refine it. When we got to where it worked well repeatably, we stopped.

I checked out precautions for higher peroxide concentrations and it looks like a huge NOPE for me (thanks for the warning), so i'll stick with this recipe until it works.. I'll try one more time with ph strips and edta-4na and better sodium bicarbonate, if it doesn't work out i'll try with pure EDTA, it seems i found one.

 

[relistan]

I checked out precautions for higher peroxide concentrations and it looks like a huge NOPE for me (thanks for the warning), so i'll stick with this recipe until it works.. I'll try one more time with ph strips and edta-4na and better sodium bicarbonate, if it doesn't work out i'll try with pure EDTA, it seems i found one.

Sounds good. Good luck and let us know how it goes.

 

[artyfarty]

Hey again.

Today i tried again with pure sodium bicarbonate and PH strips. I was using automatic stirring in this and previous attempts. I added peroxide, EDTA-4Na, stirred for a minute, added sodium bicarbonate, observed bubbling, stirred for about 5 mins and proceeded with the citric acid.

I started with 5g of citric acid (rightmost strip) that yielded 6+ph. Then i added 6 more up to recommended 11g of citric acid and got a strip very close to ph 5.
Then I iteratively added 2g, stirred, measured and tested effectiveness. I slowly reached ph 4 at total of 19g, but it still didn't work. Then i stopped.

I can see three possible answers:
* EDTA-4Na option has some unforseen complications and doesn't work that easily
* My peroxide is crappy. I don't have easy way to test it and finding peroxide test strips isn't that easy
* I'm mixing and stirring in fundamentally wrong way somehow, because i'm definetly not a chemist

Next i'll wait for pure EDTA to arrive and try with it. If it fails too, i'm blaming peroxide. Probably i'll order from another supplier, or just buy one from pharmacy...

 

[relistan]

Hey again.

Today i tried again with pure sodium bicarbonate and PH strips. I was using automatic stirring in this and previous attempts. I added peroxide, EDTA-4Na, stirred for a minute, added sodium bicarbonate, observed bubbling, stirred for about 5 mins and proceeded with the citric acid.

I started with 5g of citric acid (rightmost strip) that yielded 6+ph. Then i added 6 more up to recommended 11g of citric acid and got a strip very close to ph 5.
Then I iteratively added 2g, stirred, measured and tested effectiveness. I slowly reached ph 4 at total of 19g, but it still didn't work. Then i stopped.

I can see three possible answers:
* EDTA-4Na option has some unforseen complications and doesn't work that easily
* My peroxide is crappy. I don't have easy way to test it and finding peroxide test strips isn't that easy
* I'm mixing and stirring in fundamentally wrong way somehow, because i'm definetly not a chemist

Next i'll wait for pure EDTA to arrive and try with it. If it fails too, i'm blaming peroxide. Probably i'll order from another supplier, or just buy one from pharmacy...

Does your automatic stirrer heat the peroxide? It may be breaking it down. One simple test for peroxide is to find some zinc and add it to a small amount. Note that this is destructive. A _galvanized_ nail or similar should work. Be sure it’s zinc. If you don’t get bubbling on the surface of the zinc within a short time, the peroxide is probably bad. That won’t tell you very well how strong it is, but it will tell you If it’s pretty exhausted.

 

[artyfarty]

Does your automatic stirrer heat the peroxide? It may be breaking it down. One simple test for peroxide is to find some zinc and add it to a small amount. Note that this is destructive. A _galvanized_ nail or similar should work. Be sure it’s zinc. If you don’t get bubbling on the surface of the zinc within a short time, the peroxide is probably bad. That won’t tell you very well how strong it is, but it will tell you If it’s pretty exhausted.

Stirrer does not heat, the beaker is way below body temperature.
But getting well over 30 degrees while in shipping in this climate is quite common, and we are almost in June, soon even the air in shadow will be close to 40.

I'll try the zinc trick.