A Guide to Spirit Levels

Words: Jude Nosek
Photo Credits: SOLA

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Spirit levels are essential to producing high-quality work. In short, these tools help you determine if a horizontal surface is level or not. If you are checking a vertical surface, a level will let you know if that surface is plumb, or perpendicular, to the ground. This is why it is important to choose a high-quality level, one that is durable, accurate, and has clean, straight edges.

If you need to measure an inclined surface specifically, use a digital level, like one in the SOLA Digital Series, which not only measures perfectly level in the horizontal and vertical planes but also provides angle and inclination measurements. Here are some of the basics of using a spirit level.

How Do Spirit Levels Work?
The vial on your level contains a liquid (in the past, this liquid was alcohol-based, a “spirit”) and air. The amount of air in the vial can be exactly controlled. If the vial is acrylic, the cavity inside is shaped like a barrel. The vial is completely sealed, and because air is less dense than the liquid, air rises to the top of the barrel shape. The air bubble will always rise to the highest point inside the vial. The barrel shape of the vial’s cavity ensures that the bubble rises to the top, and the liquid completely fills the rest.

When the surface is perfectly level, the bubble will stay in the middle of that barrel shape, its edges equidistant from the markings on the vial. If the measured surface is tilted, the bubble will rise toward the higher side. This is not necessarily bad. Depending on what you’re building, a precise incline might be required, for example, to allow water to drain. If you need an exact incline, a digital level is a great choice to ensure that you are building to the desired angle.

Get Acquainted With Your Level

Consider the surface material you are leveling. If you are working primarily with metal surfaces, think about using a magnetic level. Non-magnetic levels will be fine to determine levelness, but magnets might be easier as the level can be set into position, leaving both your hands free. Not all magnetic levels are created equal. Some lighter levels (e.g., most torpedo-style and I-beam levels) have a strip magnet adhered to the leveling surface. For the heavier box-beam style levels, most have magnets inserted into the leveling surface. It can be a challenge keeping these magnets from falling out over time, as the tool is subjected to temperature changes, vibrations, and occasional abuse. Sola’s laterally installed magnets are better able to meet these environmental challenges. They do interrupt the measuring edge of the level with insertion points.

Identify the measuring edge of the tool. The measuring edge of a level is the side opposite the horizontal vial. This is important because the vial is fixed into position based on that measuring edge. The vial will be most accurate when that edge is used against the surface to be measured for levelness. The top edge of the level (the side with the vial on it) is not guaranteed to be as accurate as the measuring edge of the level. The icon guide on most higher-end levels will illustrate this.

Understand what each different type of vial measures. Most levels have one horizontal vial in the center of the level regardless of the length of the level. Levels with multiple horizontal vials are more likely to result in inaccuracies in your craftsmanship. For instance, if a level is dropped and one of the vials is accurate and one is not (even slightly), all subsequent measurements could possibly be incorrect.

How To Use A Spirit Level
Ensure your level is level. Check your level’s accuracy in the field often (especially after a drop or level impact). See below for a procedure.

Clean your level. Before measuring, use a clean, dry piece of cloth, and run it over the surfaces of your level, especially the measuring edge. This will remove any dirt or build-up from your level. Many will run a gloved finger over the measuring edge, ensuring it is clear of particles, adhesives, filings, etc.

Clean the surface of the object you want to measure. The presence of dust or grime can produce an inaccurate measurement.

Place your level’s measuring edge on the object(s) to be measured.

Make sure the level’s measuring edge is in contact (flush) with the surface from one edge to the other. If the surface touches at the ends of the level and not in the middle, recognize that the entire surface is not level. If the surface creates a lever of your level (i.e., that level teeters on a bowed surface), that surface isn’t going to be level. If you are measuring two or more points over empty air (e.g., window, doorway unfinished), ensure that the points you’re leveling have flush contact with the level.

Wait for the bubble to stop moving in the vial.

Identify the position of the bubble.

Understand The Reading
After you’ve placed the spirit level onto your surface and identified the position of the bubble, you need to understand what the position means. Remember, the bubble will seek out the highest point. These are the three readings you can get based on the correct placement:

If your bubble is in the center of the vial, then your surface is perfectly level.
If your bubble is to the right of the center lines, then the right side is higher.
If your bubble is towards the left of the center lines, then the left side is higher.

To find if a vertical surface is perpendicular (plumb) to the pull of gravity, use the same steps by placing your level flat against the object. By reading one of the vertical vials on your level, you can tell whether the object is plumb (90 degrees) or not. The object is plumb on the side you measure if the bubble is in the center of the vial.

A good choice for a spirit level is a Big Red level by SOLA. Available in different lengths and models for different jobs or measuring environments. These are very durable tools that provide extremely accurate measurements.

Three Common Mistakes That Can Result in Inaccuracies

1. Mistake: Having a level that is NOT level. Check your level often.
Accidents happen, and you might not always be there to see one go down. Any level can get damaged over time. This can affect its ability to measure surfaces accurately. Level not where you left it? Someone might have used and perhaps accidentally abused your level. So, before you get started, test the accuracy:

Place your level on a clean flat surface and make two marks: one along the edge and around the corner of your level, and one to mark the spot of the vial.
Check the location of the bubble in the vial. If it’s perfectly centered, your surface is level and this task is going to be easy. If it’s not perfectly in the center, you can still check the accuracy of your level.
Note the bubble’s location in relation to the markings on the vial. (i.e., if it’s perfectly centered, great. If it’s not, that’s okay, you are ensuring that your level reads the same in both orientations. If the left edge of the bubble is touching the line, note that location.)
Rotate your level 180 degrees around the horizontal vial, and place the level on the same surface to take another reading.
Make sure your vial and level position align with the marks you made, i.e., that the bubble stops in the same place in both orientations.
Check the location of the bubble in the vial. If the bubble is in exactly the same position as your reading from step two above, your level is accurate. If the bubble is not in the same position both times, then your spirit level is most likely inaccurate. DO NOT USE an inaccurate level.

2. Mistake: Taking the Reading at an Angle (other than 90 degrees).
If you are using the SOLA Focus Vial, you can look at your bubble from any angle, as the vial is designed with no obstructed view of the bubble. If your level has an acrylic vial with an edge, always align your eyes with the vial and take your reading at a 90-degree angle. Look exactly down or up at your vial, or exactly horizontally into the vial. The edge of most acrylic vials will optically cause a double bubble or obscured bubble effect. Observing the vial from any other position can compromise the reading and the accuracy of your measurement.

3. Mistake: Using Levels Smaller Than the Object being measured
Ideally, use a level that is as long as is practical for your work. The longer the span of the level, the better your results will be on the surface to be leveled. Using a two-foot level to determine the levelness of a 20-foot wall is not ideal because that two-foot level might miss some unevenness in the other 18 feet not under its surface. Using a longer level such as a four-foot or six-foot (or even longer eight-foot) level is recommended.

A Guide to Spirit Levels

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