See Also: Testing Your Vials

About Vials used in Carpenter's/Mason's Levels

Understanding Vial Quality
Bubbles are Perfect ...
It’s what they’re surrounded by that makes the difference!

Solid Milled Type:
(Made by Plumb-It exclusively for Plumb-It Levels)
Made using a solid, optically clear polymer, which is milled for a perfect level vial.


Accuracy in CNC milling is held to .0001” or better.
1. There is no stress movement in the material.
2. Optically there is no distortion due to “waves” or shelves that reflect and distort light. The vial barrel sits suspended clearly in its circle.
Extremely good because vial is of one solid piece construction that’s literally unbreakable.
Mounting is similar to Injected/milled types.
Viewing surfaces can be repeatedly buffed to restore like new clarity.
Weight is added because “puck” is solid and without voids.
Bubble Size is extremely sensitive to temperature changes.

Acrylic (Plexiglas)
Injected Tube Type. Found in most low cost, hardware store type levels. Manufactured primarily in the US by large manufacturers of levels.
Advantages: 360 degree reading. Low in cost, relatively durable (depending on protective cover provided). Easily replaced in the field.
Disadvantages: Accuracy is low because:
Injection molding, because of heat involved, can distort. Normal tolerances are
+/- .001" on the vial. This multiplies greatly when extended to the level's working plane.

Bubble size: usually bubble extends behind lines on edges preventing true centering of bubble.
Mounting: usually mounted into level body by means of punched slots, which can vary in their location. No means provided to adjust by rotation because slot must hold tube end.

Injected and Milled Type: Consisting of an injected core and circular mounting body in one piece, which is then milled to produce an extremely accurate barrel and highly visible line inside the body. Usually found in high-end European and US made levels.
1. Boring with todays CNC lathes, produces accuracies in the vial of .0005", which when translated to the working plane gives extremely good overall precision.
2. Vials are usually individually set by rotating them in their respective holder which is locked into the level I-Beam or Box beam.
3. A good bored finish cut on the vial barrel and line give a crisp and clear appearance. The bubble is usually held back from the lines to enable accurate centering.
Good, because vial is one piece construction, usually welded (like you weld pvc fittings in todays plumbing) to an interface which mounts rigidly to the levels I-beam or Box beam.

1. Again, Injection molding involves heat and can cause thermal distortion (movement in the material) unless extreme care is given.
1. Bubble Size is extremely sensitive to temperature, changing in length from touching lines to relatively far away from lines. This is caused by barrel walls not flexing when the vial solution expands and contracts.
2. Visibility can be poor because injection molding limits wall thicknesses around the vial barrel. Shelves usually exist above and below the long axis of the vial barrel because of shrink (thermal distortion) involved in injection molding. These surfaces, along with thermal distortion in the viewing lens surfaces can cause waves of distortion caused by reflected light.

Glass tube used primarily in Brass or Stainless Bound Wood levels.
Advantages: usually accurate, depending on manufacturer. Fixed in plaster or ceramic type material that locks its position relative to its flat plane.
Disadvantages: Reads only one direction per tube. Easily broken. Lines often cover bubble edge, making centering difficult.
See Also: Testing Your Vials
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