Before you begin to calibrate and use your pH meter you will first need to turn it on and allow adequate time for the meter to warm up. This should generally take around 30 minutes, but check your pH meter's operating manual for exact times. Take the electrode out of its storage solution and rinse it with distilled water under an empty waste beaker. Once rinsed, blot dry with Kimwipes or Shurwipes, which are available at most office supply stores. Be sure to rinse your electrode in a waste beaker that is different from the beaker you will be calibrating in. Avoid rubbing the electrode as it has a sensitive membrane around it. If you find the electrode to be particularly dirty consult your operating manual for recommended cleaning solutions. You will generally need more than one buffer for calibrating a pH meter. The first will be a "neutral" buffer with a pH of 7, and the second should be near the expected sample pH, either a pH of 4 or 9.21. Buffers with a higher pH (9.21) are best for measuring bases, whereas buffers with a low pH (4) are best for measuring acidic samples. Once you have chosen your buffers allow them to reach the same temperature as the pH meter because pH readings are temperature dependent. Pour your buffers into individual beakers for calibration. Check with your pH meter manufacturer, or current educational or professional institution, about acquiring pH buffer solutions. Buffers should be kept in a beaker for no longer than two hours. Discard the buffer when you are finished. Do not return it to its original container.

Summary: Turn on your pH meter. Clean your electrode. Prepare your buffers.

If you want to, you can put the shirt on to determine the new length. Keep in mind that your shirt will be about to 1 inch (1.27 to 2.54 centimeters) longer, depending on how wide the original hem is. Spread the shirt out on a flat, even surface, right-side-out. Use a ruler to measure up from the bottom edge of the shirt every so often. This will ensure that your shirt is the same length all the way around. If you can't find a dressmaker's chalk or pen, you can make the line using sewing pins instead; just be careful not to pin both sides of the shirt together. Keep folding your way all around the shirt. It should now be a little shorter than before. You are still folding on the outside of the shirt. Do not fold the hem on the inside. Use the zigzag stitch or the stretch stitch on your sewing machine. Make sure that your thread color closely matches your shirt. Keep your shirt right-side-out. You should now see the original hem, the hem's original stitching, and your new "seam" just above it. Focus on the new seam you made. This will flatten it, and make the bottom of your shirt smoother. If you'd like, you an secure the hem with sewing pins, although this is not necessary. Anywhere between to 3/16-inch (3.2 to 4.3 millimeters) away will be plenty.Use a stretch stitch for this step, and be sure to go back and forth over the start and end of your sewing a few times to prevent unraveling. Start sewing from one of the side seams. This will help hide the start and end of your sewing better. If you secured your hem with sewing pins, be sure to pull them out as you sew. Try to cut as close to your stitching as you can. Discard the excess material, or save it for another project. When you are done, go back over your shirt and snip off any excess or loose threads. Your shirt is now ready to wear.
Summary: Figure out how short you want your shirt to be, and make a mark on the outside of the shirt. Use a dressmaker's chalk or pen to draw a line all around the shirt at an even distance from the bottom edge. Fold the hem up until the bottom edge touches the line that you drew. Sew around shirt, as close to the selvage edge as you can. Fold hem back down, and tuck the excess fabric inside the shirt, away from the bottom of the hem. Press the hem with an iron. Top stitch as close to your seam as possible. Turn the shirt inside-out and cut the excess material away. Turn shirt right-side-out.