Vacuum Chambers - Notes and Thoughts

Posted by Ken Bandoly on Aug 16th 2019

Vacuum chambers are available in a variety of sizes, shapes and materials. Not all vacuum chambers are created equal, and neither are the resins intended for use in them. A suitable vacuum chamber should be well constructed of durable and chemical resistant materials in a manner that safely supports the extreme forces exerted on them in a deep vacuum. When choosing a vacuum chamber, you may consider some that are made from metal, plastic and perhaps glass. I can’t possibly discuss every vacuum chamber out there, so this chapter will focus on the three main styles we will find.

The most commonly used vacuum chambers for stabilization are constructed from PVC pipe. The most well liked use a clear PVC pipe for the chamber walls and stand vertically. The high cost of materials for these tend to drive prices fairly high. Available in many sizes, you can expect the cost of the chamber to increase dramatically for every inch increase in pipe diameter. While clear PVC is not required, it does provide the best view of what’s going on within the chamber. Chambers constructed from standard solid core PVC work well, however they require a clear lid in order to have a clear view of the resin surface. This is important and will be explained in greater detail later on.

A clear lid on a vacuum chamber is a tricky thing. The best clear lids are constructed from thick tempered glass, at least one-half inch in thickness. The gasket to seal the lid and chamber is typically loose or fitted like a tire around the outside rim of the glass. It is important to note, In the case of tube style chambers, there should be no holes made in any clear lid. Fittings, valves, gauges etc. should all be mounted high on the chamber walls. The holes created in a flat clear lid will weaken the material and greatly increase the likelihood of catastrophic failure. It is interesting to note that ever growing acceptance of marijuana for medicinal and recreational use in the US has considerably increased the market options for vacuum chambers. An ever-growing number of vacuum chambers incorporating Pyrex style dishes, aluminum or steel pots and acrylic lids are showing up at very low and enticing costs. Often times, these chambers are sold in combination with a small, off-brand single stage vacuum pump. If you’ve ever heard the expression “you get what you pay for,” this is a prime example. The depth of vacuum and the length of time required to make an herbal extract or marijuana concentrate is considerably less than is used for stabilization. Therefore, these economy version deals do not need to be as durable or reliable as we need.

The affordability of home manufacturing has most recently affected the vacuum chamber market considerably. There are now a series of chambers available which are seemingly middle ground between herbal extract and stabilization. These chambers are typically slightly larger and sometimes a bit more durable than the herbal economy chambers for degassing epoxies and rubbers, but like their cheaper siblings, these chambers are characterized by a weaker acrylic lid with gauge and fittings attached to it. These degassing chambers are slightly more durable, but also not intended to hold as deep of a vacuum for the length of time necessary for stabilization.

As woodturning and home stabilization continue to be one of the fastest growing hobbies in the US, the companies that make and/or sell these two types of chambers have undoubtedly seen a very large number of warranty claims made for chambers that failed when used for stabilizing wood. It is now not uncommon to see disclaimers such as “not for stabilization” or “for degassing epoxies, urethanes and rubbers” on the product listings.

Although most have gone to cylindrical chambers, it is still possible to find cubic form chambers. Typically constructed from acrylic sheets, the weaker design of flat walls vs the strength of a cylinder and likelihood for acrylic to be affected by the resin have this design obsolete. When choosing a stabilizing chamber, here’s a list of things to consider:

  • 1.Does it provide a clear view of the resin surface?
  • 2.Does it use acrylic, which is best to avoid?
  • 3.If acrylic or glass lid, are the fittings in the lid or in the chamber wall?
  • 4.Does the size support my project material, with plenty of room above?
  • 5.Does the chamber I need fit my budget?
  • 6.Is the chamber safe and reliable and the company reputable? Has anyone used it before? (look for mentions, reviews and discussions on forums and social media. If you cannot find any information on them and still have questions, there are several places on the internet to find support. See the appendix for online resources.)