Hydrogen peroxide 3%?

[dendro king]

Hello orchid lovers,

A question for those who have used hydrogen peroxide before during flasking, is 3% enough? ( pic attached)
So that I can flask the seed in the media, then spray some peroxide and leave in bright light for 24 hours, and maintain a sterile flask. Or would I need more than a 3% soloution, thanks, Jack.

[Silje]

I use a 10% solution. 3% sounds little...but I haven't tried to weaken the solution so I've no idea...

[Roey.P.]

It's enogh usually anyone will advice to mix 6% with half size of water to get 3%. Because usually it's strong for some seed higher then 3% ten minutes and can kill them and 3% is enogh. Good luck I have flasked myshelf.


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[Coldgrower]

I am experimenting right now with 3% and 6% H2O2. So far every one of the 3% flasks has contaminated. on the other hand none of the 6% flasks has so far contaminated. Seems to me you either need to leave the seed in for a long period of time or use a stronger solution.

[dendro king]

I bought a 6% soloution and so far so good

[Coldgrower]

I wish I could get 6% H2O2 here in the States! It seems to be only available at Beauty supply stores but it has the addition of H2PO4 Phosphoric acid. I don't know how that addition will affect the PH of the agar medium.
I am experimenting with two different terrestrial genera, guess I'll have to wait and see.

[Silje]

Originally Posted by Coldgrower

I wish I could get 6% H2O2 here in the States! It seems to be only available at Beauty supply stores but it has the addition of H2PO4 Phosphoric acid. I don't know how that addition will affect the PH of the agar medium.
I am experimenting with two different terrestrial genera, guess I'll have to wait and see.

You can't get it in the pharmacies? That's where I get mine. I can get various strengths from 5%-40%. Stocked where the disinfectants are.

[Coldgrower]

Originally Posted by Silje

You can't get it in the pharmacies? That's where I get mine. I can get various strengths from 5%-40%. Stocked where the disinfectants are.

Nope! no one carries just H2O2. I did find it at a biological supply place, they will only ship to institutions and businesses...

On an unhappy note, one of the 6% flasks contaminated. I noticed it last night. That means there is only one 6% flask uncontaminated, and I'm still left with the dilemma that NaOCl as the best sterilant for most species.

[Silje]

Originally Posted by Coldgrower

On an unhappy note, one of the 6% flasks contaminated. I noticed it last night. That means there is only one 6% flask uncontaminated, and I'm still left with the dilemma that NaOCl as the best sterilant for most species.

Hmmm...sorry to hear that. I've actually been using 10% solution myself. I can't tell you how I decided on that strength and from what I've read it's a bit of an overkill. Might even kill some seeds, I suppose.

But, I also do not have any contamination, except for:
1) In a certain flask that I assume just doesn't seal well enough. I tried to compensate by using sellotape to strengthen the closing mechanism, but I don't think it worked. Unused flasks of the same type has been drying out so they're definitely not completely sealed.

2) When I sown too dense. I've had a couple of accidents dropping too many seeds into flasks. They germinate into a heap of protocorms and reach a certain stage before they turn yellow and die off.

3) I've had no success with some old NOID phalaenopsis seeds, but it could be that the seeds are not viable rather than that the solution is too strong, because all the flasks with catt seeds have germinated, and if they're in a sealed/good flask and not sown too dense, they've stayed clean all of them.

[Coldgrower]

Silje,

I've started putting my flasks into zip bags after sowing and in storage. Our summers are humid and my basement gets damp. the zip bags are an additional defense against contamination.