Back to testing methods - over or against?

[Scoot]

Brought this up awhile ago - what's the preferred method for reading Nitrate test results, at least for AP test kits? Either against the card, or held over the card.

With my nitrate test tube against the card, I see a 5-10PPM reading. With it held over the card, a half inch or an inch or whatever, I think its reading close to zero. Both methods in bright light. I even took it outside in the sun to verify. Same difference.

I see this with pH tests too - against the card is an 8.2, over the card is an 8.0.

I know several of you chimed in on this before. I can't tell from the instructions, does any know the definitive method to read results?

 

[roka64]

Probably the way to get the best answer, would be to call them. Is there an 800#, for customer support?

 

[Tex]

I've always put my test tubes against the white background just to the right of the color bars and tried to match the color on the left. When possible, I check it in sunlight. I agree, the instructions are ambiguous.

 

[swjunkie]

just said the exact same thing on my other post with my PH when I hold it against the card I get 7.8 when I stand it upright on the card I get 8.2. So I am going with it upright.

 

[Scoot]

LOL, swjunkie, I get a reading in-between against/away, when I stand it up.

Haven't called yet, but I probably will.

 

[swjunkie]

I think we need to make our own test kits. Maybe we can call the companies and give them some input. (from people that use these tests on a regular basis).

 

[Scoot]

I've contacted AP, but over a day now and no response. I've called the tech support line, left a message too.

I'm really curious about this - my nitrate readings are low enough that I'm showing a clear ZERO when I hold the tube over the card, but 5-10 when held on the card.

I don't want to use the method that gives me the results I want

My pH tests are always right-on when held against the card, but a little low when held away.

 

[swjunkie]

Took my water in to the LFS and they tested it at 8.1. and thats closer to the 8.2 I was getting when I stood the tube up on the card.