DIY Vacuum Chamber for Sous Vide and the Kitchen

104,123

144

52

Posted in HomeKitchen

Introduction: DIY Vacuum Chamber for Sous Vide and the Kitchen

This is my first attempt at a DIY home vacuum chamber for sous vide and marinating food in the kitchen.  I spent about $170 including the cost of a new vacuum pump.  Here's a demonstration:

The chamber is a flat piece of high quality plastic (polycarbonate) laid on top of a flat pan or bowl.  Rubber matting is used to create a gasket between the pan and plastic.  A normal automotive pump then sucks out the air.  With this simple setup I can pull a vacuum to 29" of mercury according to the cheap gauge I have, which I understand is better than commercially available vacuum sealers.

One of my goals was to have a setup where I could re-use the bags.  Instead of heat sealing plastic bags I put the food in Ziploc bags with the slide sealer.  I then use magnets on each side of the polycarbonate to close the bag inside the chamber once I pull out the air.

See my inexpensive DIY sous vide controller for the other half of sous vide.

Step 1: Obligatory Safety Mesage

Before you start out, there are two things you need to keep in mind:
  • If you use a good vacuum pump you are dealing with very high pressure.  Atmospheric pressure is over 14 psi which doesn't sound like much until you realize that  1-foot cube has just over a ton of pressure on each side.  I crushed a thick metal pan (see picture) that I thought could handle the pressure.
  • Keep your fingers away from the air-intake of your vacuum pump.  It will tear or rip off your skin in no time.  You are a complete moron if you check to see that your vacuum is working by using your fingers to feel for air.  Do not ask me how I know this.

Step 2: Materials and Tools

Materials:
  • Vacuum pump.  I bought a Robinair 15310 VacuMaster from Amazon for $106.
  • 1/2" thick polycarbonate (AKA Lexan).  Mine is 18"x13" for $24 at a local plastics shop.  A small piece of polycarbonate for practicing is recommended.
  • Plumbing: 1/4 inch NPT fittings, all from Amazon
    • Male nipple $7
    • Female tee $7
    • Inline ball valve with hose nipple. $16
    • Vacuum gauge $9
  • Teflon tape $1.50
  • Nylon tubing to fit over ball valve nipple $8 at HomeDepot
  • Nipple for attaching hose to vacuum pump $2 at HomeDepot
  • Some sort of rubber mat.  Mine is HomeDepot "Grip liner" for $5.
  • Something strong and air-tight to use as the vacuum chamber.  I've been using a frying pan.
To implement my scheme for closing the bags:
  • Some rare earth magnets (I used 1" magnets I had laying around)
  • Small nylon washers
  • Plastic epoxy.
  • Paper clips
  • Freezer-quality plastic slide-seal bags.
Tools:
  • Drill (preferably a drill press) and 7/16th drill bit.
  • 1/4" NPT pipe tap $9 on Amazon.
  • Spray bottle with soapy water.
  • Scissors or razor
Notes:
  • Half-inch polycarbonate may be overkill but it's better to be safe than sorry.  (Polycarbonate is used to make windshields for jet fighters.)  Even at a half-inch thick I can see it sag a little bit when the vacuum gets near 29" inHg.
  • My piece of polycarbonate is obviously a lot larger than the pan I use in the demonstrations.  I made it larger because I may want to try to make a larger chamber.  You can use a smaller piece.
  • The vacuum chamber I bought appears to be middle-tier on Amazon (i.e. there are cheaper and more expensive).  I got this one because it evacuates air at 3 CFM which is more than most (many are 1-1.5 CFM) and thus faster.  It takes about 5-10 seconds to get to 29" inHg  with this pump.

Step 3: Drill and Tap Polycarbonate

Drilling the hole in the polycarbonate is much easier if you have a drill press because you'll likely need to pull out the bit multiple times to clean the plastic off the bit.  It will help if you practice on a scrap piece of polycarbonate so you can learn what to expect.  It's not hard but polycarbonate is expensive enough that it sucks to screw up.

Figure out where you want to drill the hole.  You probably don't want it directly in the center because the gauge and tubing will get in the way when you seal the bags.  According to the manufacturer of Lexan you can use a general purpose bit at a low speed if you keep it lubricated (see PDF here).  Keep the bit and hole wet with soapy water and you'll be fine.

Tapping the hole is just a matter of screwing your tap into it.  Keep it well lubricated with the soapy water.

Step 4: Assemble the Hardware

Assembling the tubes is easy.  Be sure to use Teflon tape in all the joints.

Step 5: Create Gasket

Cut up the rubber matting and put a hole in the middle to act as a gasket.

Step 6: Prepare the Bags for Sealing

To close the seal inside the chamber I needed a way to attach the slider to a magnet.  What I've done so far is glue plastic washers to the slider using plastic epoxy.  Leave enough of a gap so that you can thread a paperclip through the hole.

Step 7: Operating the Vacuum Chamber

You can see how this works in the video on the first page.
  • Attach the magnet to washer on the bag.
  • Tape the bag to the side of the chamber (pan).
  • Put the gasket in place and cover the chamber with the polycarbonate.
  • Place your other magnets over the inside magnet.
  • Operate the vacuum pump until you get your max chamber.
  • Slide the top magnets.  The inside magnet will close the slide sealer.

I keep the other magnets in the plastic film because it makes it easier to work with them. 

Step 8: Effectiveness

For the most part this setup works very well.  There are two areas that could use refinement and I'd love to get some ideas on how my design can be improved.  Please leave comments with your thoughts!

1) The method of sealing the bags is a bit awkward.  I want to keep the ability to re-use bags but I'd like a more robust method for sealing them, preferably without having to glue anything to the bags.  I had some frustrating moments when the washers broke off from the slider.

I'm not against using a heat sealer if it's a supplemental method (i.e. I can either use Ziplocs or heat-seal).

2) The result of the packing is very tight if the item is dry (like in the demonstration video).  When I seal wet food, though, there is a little bit of air left in the bag after sealing.  I believe what's happening is that water is boiling off of the food when it gets to near-vacuum and gets trapped in the bag as water vapor.  I've tried chilling the food and even freezing it before sealing but the result still isn't as good as I'd like.  I believe this is more of a technique problem; perhaps I need to seal the bag and immediately release the air.  How to commercial vacuum chambers deal with this?

Food Science Challenge

Finalist in the
Food Science Challenge

Share

    Recommendations

    • Colors of the Rainbow Contest

      Colors of the Rainbow Contest
    • Woodworking Contest

      Woodworking Contest
    • Flowers Challenge

      Flowers Challenge
    user

    We have a be nice policy.
    Please be positive and constructive.

    Tips

    Questions

    52 Comments

    Since you're using a pan for a chamber the sealer is going to be tough to modify. I used two stainless steel chafing dishes one in the other as a chamber and cut out the top cover and added the Lexan sheet to that. Silicone sheet on the sealing lips provided the seal. That gave me a solid tight chamber 11 inches by 18 and 9 tall. I did not put any gauges or nipples on the top and chose to port the hose barb through the back side. That leaves the top clean and free of hoses and fittings.

    I used an Edwards M8 pump which will pill 7 cfm and down to 10 microns or less. The pump runs to a 250 ml trap with silicone gel in it. The top of the trap has the gauge ( electronic set to microns ) and the continues to the chamber. I bought an old Food Saver vac and pulled the seal bar assembly out of it and mounted it in the chamber. I modified it to 6 mm heat strips. I remoted a heat control switch to the front of the chamber.

    To use I put the food in food saver type bags ( must have the diamond ripples ) and lock it into the food saver seal assy. is the chamber. I place on the top and crank down the chamber. When satisfied with the vac I operate the heat bar via the remote dial. Works well and will crush a steak if you pull it way down. Prior to that I used a clumsy O ring rod and seal to operate a bag pull inside the chamber. It worked but ziplock bags fail after a short time.

    Simply brilliant, thank you for sharing!

    Wow, this is an incredible design! Thanks for the detail. Did you ever find out the solutions to the issues with the water vapor and bag sealing?

    1 reply
    user

    Thanks! No, I've never figured out the best way to seal wet food. At this point most of my sous vide doesn't require a strong vacuum. I use the "poor man's" method of dunking the bags in water and zipping them closed. It's something I'd like to explore but other projects get in the way. :)

    I'm amazed you can get 29" of mercury! Most of the vacuum pumps i'm looking at that are 300-400 dollars can only pull about 23-24 inches of vacuum. Can anyone shed light on this? I'm looking at making a degassing chamber for silicone and other liquid materials, and I was wondering if this is enough of a vacuum?

    2 replies

    I have a low-end commercial chamber vacuum sealer. The strongest vacuum it can put typically is about -27" of mercury (assuming the gauge is correct). If there is any moisture in the bag, then it should be chilled before sealing. The warmer the liquid, the higher the pressure at which it will start boiling. And you don't want any boiling when you are sealing bags. Boiling liquid will prevent bags from sealing properly and will not evacuate as desired. Some people even complain that if you seal raw chicken in a bag when it is too warm, the water boiling off from its skin will change the texture. Boiling while sealing bags is a bad thing.

    user

    According to the specs on the pump it can pull a vacuum to 750 microns which is way more than necessary (I assume) for a good vacuum chamber.

    Nice instructable

    I have a commercial vacuum sealer and i have some experience, regarding some questions that are in the room.
    There are two controls. One is for the vacuum, the other for the time of the sealing heater.
    Depending on what you pack, you have to adjust the vacuum.
    If you have free liquid, you can't set it too high, otherwise it starts to boil. There are no tricks, to circumvent this, it's physics.
    http://en.wikipedia.org/wiki/Vapor_pressure



    The pressure on the outside is reciprocal to the vacuum. (1000g per square centimeter at a theoretical total vacuum 0 hPa)
    Since you never reach a total vacuum, it will be less than 1000g. But then, at 10 hPa or mBar, you still have 990g.
    That is close to a metric ton on a square foot... even if you are far away from a "total" vacuum. (compared to vacuums, used in thin film deposition or semiconductor production, which is around what you have in space)

    To reach such vacuums, you need massive diameters in the "pump tubing"(actually stainless steel pipes with a diameter of 2-3 feet), otherwise the molecules don't find the way into the pump. (molecular flow) Funny behaviour..
    Because of gassing out, you are very limited in the materials used. Stainless steel, teflon and even gold as gaskets...
    And yes, i worked on such equipment.

    http://en.wikipedia.org/wiki/Vacuum






    The sealer should be a flat heater type, not just a wire.
    It should be 2-3mm wide and covered with a teflon tape. (The brown tape in the picture.)
    This way, it even securely seals, if there is liquid inside the bag.

    One commenter suggested, that it would help to have some sort of mesh in the bag. This isn't needed, for these types of vacuum sealers.

    For the cheap "vacuum" sealers, with the bag at atmospheric pressure, during the seal, you definitely need a meshed bag.
    But then, most of these sealers are only toys.

    Pictures of the sealer and sealed selfmade "Weisswursts".

    IMG_20101124_185613.jpgIMG_20101222_214201.jpg
    6 replies
    user

    Thanks for the comments. So if I understand you correctly, you think my vacuum might be too high for wet food? So maybe I should try for ~27 inHG instead of 29 inHG?

    The pan I'm using in the video is aluminum. Do you see any problems with out-gassing using aluminum?

    Yes, the vacuum may be too high for wet food, if it starts to boil.

    I'm not familiar with inHg, but from what i looked up, 29.5 inHg has to be "total vacuum"? Then 27 is less, right?
    Although, 29.5 is atmospheric pressure an 0 is vacuum most of the time

    On some old vacuum meters, we had Torr as unit, which is mmHg and 760 mm equals atmospheric pressure at sea level, 0mm is "total vacuum".


    With my vacuum sealer, i set the vacuum by trial and error. Depending on the goods to seal.
    When i put a cup of water inside, the pump won't stop, if i set the vacuum too high. (The water boils)


    The out-gassing of aluminum isn't a problem at these pressures.
    The top cover of my vacuum sealer is cast aluminum as well.

    This is only a problem at high to ultra-high vacuum, where you essentially have to count molecules, to measure the pressure.



    Don't you want it to boil it a bit here though?

    Isn't the idea to replace the air with water vapour, and then when you re-establish the pressure, the water vapour recondenses, and you have removed the air?

    I would think that adding a small amount of hot water in a little cup or something beside the food or even in the bag is actually desirable.

    No, it doesn't work that way.

    Water vapour has a huge volume, in comparision to liquid water.
    This volume needs to to be pumped by the vacuum pump.(your pump won't be big enough, except you whipp up some serious cash...)
    If this happens for example on our Weisswursts, their skins rip.


    At least not in food packaging. The idea behind vacuum sealing is to remove as much air from the packaging as possible.

    If you want to keep the food from oxydising, you need to remove as much air as possible from the package.
    On the long run, this only helps, if you use bags with a oxybarrier. (Those bags mostly have a metallic appearance.) Standard PE bags won't do, polyethylene is oxygenpermeable.

    Food preserving in combination with vacuum sealing also requires immaculately clean procedures.
    Vacuum sealing alone won't do. You will need a preserving technique, like pasteurizing, brining with salt, or adding food grade preservatives like sorbate and so on(not my choice).

    For example: the Weisswursts on the picture have been vacuum sealed hot(pastuerizing temp) and cooled in a ice bath in the bags.

    The smoked salmon has been brined with salt and smoked. Brining removes free water from the salmon and adds salt.
    Together with the smoking and cold storage, the salmon keeps at least for 8 weeks at temperatures above freezing.

    By the way, brining fish and meat in a vacuum bag is a really elegant way for small batches.

    You're not quite getting what I'm saying. I'm not saying to boil the food, I'm saying boil a few cc of hot water placed in the bag ON TOP OF the food. That way the (small number of litres) of steam will wash away the air as you pump it down, Then when you seal the bag the bag will contain virtually no air.

    If you intend to vacuum moist goods, this will happen anyway, if your vacuum gets too high. (with the chance of bursting of the goods)

    For dry goods like herbs or teas, you don't want any moisture inside. You can set your vacuum higher here.

    I think i get your point, but i really don't see a positive effect.

    where did you find a vacuum gauge for $9 i need one for my freeze dry machine but cant find it for less then $20

    2 replies
    user

    It looks like the one I bought is no longer available at Amazon but here's one that's $9: http://www.amazon.com/gp/product/B004KFKYPM/ref=oh_details_o01_s00_i00

    They have cheaper ones; look in the "Customers Who viewed this item..." section.

    thanks I must have been searching the wrong phrase there are a lot on there.

    Great work but I'd like to add one word of caution: The reason medical and food grade pumps are twice as expensive is because they are made to keep the cancer causing chemicals from the pump lubricant from running up the vacuum line. This is a very serious issue when you are potentially contaminating your food. May I suggest that you make an adsorbent filter plus a cold trap in the line and also that you only use food grade tubing. Smell your tubing after a dozen uses, does it smell like something you should be eating?

    1 reply

    I don't think this is a huge issue in this case. Keep in mind that the vacuum hose doesn't connect directly to the bag - just to the chamber housing. Unless the lubricant vaporizes in the low pressure environment I'd say the chance of contamination is relatively low.