While on a recent customer visit we were offered a tour of their packaging test lab. While passing through I noticed a lab technician repeatedly pouring the contents of a bottle into a graduated cylinder and making a tally mark on a sheet of paper for each time the cylinder was filled until the bottle was completely empty. The lab technician then told me they were checking the Over Flow Capacity of the bottles. I must have looked like I didn’t understand as he proceeded to explain their process. To get the most accurate reading they would divide the OFC specification by 10 and use the closest sized graduated cylinder to that number. They would then add the 10 data points to get the total capacity. He explained that this method would provide a more accurate reading then just using one larger graduated cylinder as the larger the cylinder the larger the range between the calibrations.

It was interesting how they used the graduated cylinder but seemed like a lot of work and there must be some error as there was still a bit of water left in the cylinder between fillings and I wasn’t too sure how accurate the graduation makings were. I suggested that there was an easier, quicker and more accurate method to measure the OFC and it only required an electronic scale. First we proceeded to weigh the container in Grams, keeping a record of the number, we now knew the weight of the container. Next step while leaving the container on the scale tare the scale out till it reads zero. Then completely fill the container with water and record the weight of the water in Grams. Since a Milliliter (ml) of water weighs one (1) gram we can calculate the capacity of the container by knowing how much the water weighs. For example 8 ml of water weighs 8 grams. It’s very important to leave the container on the scale and tare it out because we want the weight of just the water not the container and the water. It’s that easy, the weight of the water in grams equals the volume in ml.

Next time when measuring OFC leave the graduated cylinders in the cabinet and use the scale.