Ordinary 3% hydrogen peroxide from the drug store should work.

My understanding is that instead of relying on subjective color change the baseline of the reaction solution should be a ph of 5.0. After the test you measure the amount of sodium hydroxide required to get back to that 5.0 ph and multiply that amount by 16 to calculate ppm of SO2. Being able to use a precise ph meter measurement vs observable color was game changing for me.

Yes pH should go from about 3 to above 7

It is possible that the hydrogen peroxide is stale. I recommend trying the test after Purchasing new hydrogen peroxide and fresh distilled water. I experience the same issue but a little Noah gives the base colour I want to start with. It is a greenish gray. Of course the measurements must also be accurate. I like this system for general measurement but I sent my samples to a lab for best accuracy. Since the easiest and least expensive components are available at any druggist I would start there. Don’t give up it is a good system.

I have the same issue with the peroxide and water solution staying bright pink. I find that it takes 5-10 ml of NaOH to bring the color to the tipping point between gray and green. If you are sticking to the printed directions with the expectation that 1-2 ml will do the trick keep adding more until you get that color change.

I had the same problem using the HP that came with the kit. Redo with new HP.

If you were able t "calibrate" the reaction solution in the beginning the hydrogen peroxide should be good You can always replace it with some purchased from your local drug store - as long as it is 3% (it's the same thing). I found it easier to see the difference by doing the calibration & test on white paper - it makes it easier to see the color change

Use this kit regularly. I have found that 3% hydrogen peroxide can be purchased from a regular pharmacy or drug store. It is slightly acidic thus the pink color at the start. Yes I have to add NaOH to make it neutral (until the pink turns gray). If you can't turn it neutral then either your hydrogen peroxide has become contaminated (this can happen easily if you place the dropper/pipette you used from the acid into the hydrogen peroxide). But if you can get the hydrogen peroxide to neutral by adding NaON but you follow the rest of the instructions and don't get a color change it may be (1) you have no free S02 in your wine or (2) you don't have a good seal on the stoppers or (3) the glass pipette is pressed down into the glass to far so the gas is not moving from the first to second.

When you added the NaOH what color were you aiming for?

Is your Hydrogen Peroxide old? It goes bad over time so if it’s been on the shelf awhile that could be the problem . I bought new hydrogen PE (its cheap) and it seemed to give me a crisp color change.

Hi Patti I am not a chemist but it would be my guess that your reagents are spent. The hydrogen peroxide does not last long. I have long since obtained new regents except the indicator. I bought 30 % hydrogen peroxide and had to dilute to get 3%. It was very strong and almost green when I added the 40 ml of water so I had to use the HCL to get it back to pink and then NAOH to get back to the gray almost green color. It’s very important to get to this point or the test will not work right. Once again I believe that your hydrogen peroxide is bad.