Your numbers sound fairly believeable. Litmus paper was the standard way to test ph many years ago. They made a ball of moist earth, broke it in half, and then pressed the ball back together with the paper in between and waited 20 minutes. I wouldn't add any water to the soil as the water might affect the results.

That the peat tested at a pH of 6 should be an indication that something is wrong, although the pH of peat can range from 3.6 to 7.6.
The standard used by laboratories for pH is distilled water, which is what you should be using since your tap water can adversly affect your results.

Thanks for the input: it sounds like I can believe the paper, but that the water I use, and how much of it, should be modified.

I would wonder if adding ph 7 water might raise the reading in acid soil.

Peat can vary a lot.

On second thought, if the water was pure, it shouldn't affect the results as it would add no ingredients.

wayne: I was wondering the same thing, I guess the difference between neutral tap water and neutral distilled water is the dissolved solids, which might affect the reading with the former, as others have suggested...

I also would not base the validity of these results on the peat reading alone...

How did you determine your tap water was pH 7? What was your control? In the lab, using a very good pH meter, if you "zeroed" it using a substance that was the control. If you "zeroed" the meter at 7.0 with tap water then everything else would be off, depending on what the pH of that tap water was. In the water quality lab various substances of known pH were often used to verify the accuracy of the pH meter, buffered solutions.

The tap water was the first thing I tested with the strips... I see your point of a control. I vaguely remember doing titrations in the lab, setting control, adding a buffer to a solution until it turned a certain color, etc.

I guess the thing is that if I really want a very accurate result I will have to use distilled water with an expensive meter, which I'm not sure I want to do. I was hoping I might get an estimation using these cheapo strips, which I still think might be possible. Actually, the original reason for my testing was to determine if the scoria I just collected is a safe pH for the garden, and not too alkaline.

When I took soil science at university many decades ago we added the soil to a container with water and shook it up several times over a couple of weeks and then tested the pH with pHydrion paper. ( I think someone is now marketing something like pHydrion paper as ''Litmus" paper. )

The reason for waiting a couple of weeks was to allow buffers (A function of cation exchange capacity and complicated.) in the soil to do their thing.

IMHO, because of buffers the difference between tap water and distilled water should not make a significant difference after a week or two.

"Accurate" may be too strong a term. Litmus paper will give you a general indication that material "A" is more acid than "B", but doing color comparisons with a piece of damp paper and a chart leaves a lot of margin for error. The numbers you list are well within the realm of believability, and may in fact be accurate, but without a known entity to use for calibration, it's pretty subjective.

pHydrion is a brand name of one of many litmus papers made.
Litmus papers give you a general idea of what your soils pH may be but tell you nothing about why it is where it is. What is the level of Calcium? What is the level of Magnesium? What is the ratio of Ca to Mg? Soil pH is of little value unless you know more about the why.

Thanks again for all the input...

So I finally got some distilled water and it tested at 6 with the strips! So now I'm guessing that my original results were all off if the paper shows 6 for what is really neutral. This means the scoria I was most concerned about testing, could be at least 8. My original idea to test the scoria was some info online which said that red scoria lowers pH below 7 and black scoria raises it above 7 because of lime content. The scoria I collected is black. I guess I should have collected the red variety which is also found in the area...

So I'm thinking I'll save the black scoria to use in potting mixes with peat and compost, but get some red scoria or maybe some light gray pumice to try in the garden. Does this sound like it makes sense?

Where do you find the scoria? It sound like it could be a fun experiment.

Hi tishtosh, I got the scoria from the Caja del Rio plateau at the extreme western edge of Santa Fe. It's BLM land, and there are also a couple of quarries where they get the red scoria used on icy roads.

I'd like to make my own potting mixes and avoid having to buy the expensive little bags of stuff from the store all the time. I'll see how scoria and compost work, and then I'll have to make a lot more compost than normal.

For anyone interested...

Here are the latest litmus results after using distilled water to wet the materials overnight before testing...

Recall that the litmus was showing distilled water which we know is neutral as a pH of 6, so I've added one point to get the following...

peat: 7
homemade kitchen compost: 7
red scoria: 7+
tap water: 8
black scoria: 8+
fresh horse manure: 8+

i know these results are not very accurate, but I still feel comfortable mixing the black scoria with compost or peat to make a potting mix, but I'm not as comfortable now using the black scoria as a garden amendment; instead I'll use the red, which seems to have a nicer, lighter, more porous texture anyway.

The horse manure that I've been using extensively in the garden (never thinking about it's pH before), I am considering composting together with gypsum before adding to the soil. I'm not going to change everything I do based on this shaky litmus paper, but I think it's enough evidence that I should modify things slightly. Any comments on this?
Thanks