On The Level: Keson and SOLA: The Ultimate Guide to Using Spirit Levels

Words: Todd Fredrick

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’s important to choose a high-quality level, one that is durable, accurate, and has clean, straight edges.

Before you start your next project, make sure you have a good quality tool. If you need to measure an inclined surface specifically, you can use levels such as the SOLA Digital Level, which measures in the horizontal and in the vertical plans, and can provides angle and inclination measurements.

Here’s are 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 as 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, it’s edges equidistant from the level markings on the vial. If the measured surface is tilted, the bubble will rise towards the side which is higher. This is not necessarily bad, because 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.  
  • Identify the measuring edge of the tool. It is the side opposite the horizontal vial. This is important because the vial is fixed into position based on that measuring edge. That vial will be most accurate when that edge is used against the surface to be measured for levelness. Don’t use the top edge of the level as the measuring surface. 
  • 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

  1. Ensure your level is level. Check your level’s accuracy in the field often (especially after a drop or level impact). See below on a procedure . 
  2. 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 clear of particles, adhesives, filings, etc. 
  3. Clean the surface of the object you want to measure. The presence of dust or grime can produce an inaccurate measurement.
  4. Place your level’s measuring edge on the object(s) to be measured. 
  5. Make sure the level’s measuring edge is in contact (flush) with the surface from on edge to the other. If the surface touches that 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., fence posts tops), ensure that the points you’re leveling have flush contact with the level. 
  6. Wait for the bubble to stop moving in the vial.
  7. 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:

  1. If your bubble is in the center of the vial, then your surface is perfectly level.
  2. If your bubble is to the right of the center lines, then the right side is higher.
  3. 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.

3 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:

Testing Vial Accuracy:


  1. Place your level on a clean flat surface and make two marks:
    1. One along the edge and around the corner of your level, and
    2. One to mark the spot of the vial.
  2. 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.
    1. Make sure your vial and level position aligns with the marks you made, i.e., that the bubble stops in the same place in both orientations. .
  3. Check the location of the bubble in the vial. If the bubble is in exactly the same location 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 views. 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. Reading from any other position can compromise the reading and can ruin the accuracy of your measurements.

3. Mistake: Using Levels Smaller Than the Object being measured

Ideally, use a levels that is a long as is practical for your work. The longer the span of the level, the better your results will be on a the surface to be leveled. Using a two-foot levels 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. A longer, four or six-foot level would be recommended. 

Which Spirit Level Should I Use?


Here are some spirit levels from SOLA that you can use for different measuring needs:

For Horizontal and Vertical Measurements

For Angular Measurements

For Measuring Small Spaces

With this guide on how to use a spirit level, you are set to get accurate measurements for your job. Whether you’re a carpenter, mason, plumber or a layperson, you can now work on repairs, construction and plumbing jobs easily and accurately.
For more information on where to buy SOLA spirit levels, click here to contact us.

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