(06/23/13 UPDATE: Be sure to read the update at the bottom of the page about the subsequent testing we did using a meta-aramid type gasket. Read the update if you don't know what meta-aramid is.)
(07/20/13 UPDATE: We have a second update regarding a small addition to the Eggware cap and their plans to deal with the melting gaskets. See the bottom of the web page.
We first learned about this new accessory on one of the Big Green Egg forums where a poster was asking about troubles they were having getting to high temperatures when using this device. That sounded like a challenge to us and a grand opportunity for a product review, so we purchased one and here we are.
This cap will fit Medium, Large and Extra Large Big Green Eggs, Big Joe and Classic Kamado Joe cookers, and the Primo Oval Jr and Oval XL cookers. The touted benefits of this device are:
The unit is made in China from 304 stainless steel and looks well made and is certainly more attractive than a galvanized chimney cap from the hardware store that some cooks have used. It comes with a felt gasket that attaches to the chimney of your cooker to provide an air-tight and secure seal between the cooker and the cap. We did all our testing without the gasket, except then we did, but then we didn't, but you'll just have to keep reading. Here are a few views of the Eggware cap:
Here are some photos of the original gasket. It is a felt material very similar to that used in the original Big Green Egg gaskets. The first photo shows the gasket and its backing tape. One side has an adhesive on it covered by the tape. The second photo shows a closeup of the gasket material.
We didn't intend to install a gasket on the chimney of one of our cookers in order to test the cap, so we did all of our testing without the gasket, until that is, we started testing with the gasket. But, you'll have to keep reading. However, without the gasket, we had no problem with the cap staying on the cooker (we ultimately decided to use a medium Big Green Egg cooker for testing). Nor did we have any trouble getting the fire to go out after we were done. After having played with the cap for a while and building a fire and snuffing a fire, we were prepared to say that we saw no need for a gasket. But then, well, you'll just have to keep reading.
The first thing we wanted to try was to see how hot you could get your cooker with the cap set to its maximum opening. A poster on one of the Big Green Egg forums had said they couldn't get their cooker beyond 450° with the cap on and fully open. We actually were able to get our medium Big Green Egg up to 895° with the cap on and fully open. It seems like the poster was having the usual airflow problems, totally unrelated to using the Eggware cap. We then took the cap off and the cooker continued rising to 1013°, so it is certainly possible to get a cooker almost as hot with the cap on as you can with no cap at all.
We then, just for fun, tried a few different settings of the vent opening to see what sort of temperatures were associated with different amounts of venting. We let the cooker stabilize at each vent setting and took a photo. The lower vent of the cooker was wide open:
So, yeah, it gets plenty hot with no difficulty whatsoever. So then, the next question one might ask is safety related: How hot does the cap itself get, since it is made from stainless steel, a very good conductor of heat? After all, one of the things touted about ceramic cookers is that they don't get as hot to the touch as metal cookers. The following highly technical drawing in the style of Alton Brown shows how hot the surfaces of the cap got while the cooker was roaring away at almost 900°:
So, yes, it gets very very hot. Not to mention the incredibly hot air venting from the cooker. You would do well to keep hands away from the top when in use. If you plan to adjust the vent opening, you probably want to use something like your ash tool or grid lifter to tap the tab and make your adjustments. If you plan to remove the cap while the cooker is roaring away, you'd best use some very good insulating gloves or pads and keep your arms and hands away from the column of hot air shooting out of the top of the cooker.
So, if you have been patiently waiting for us to get to the "just keep reading" bit, your patience will now be rewarded. As you have read earlier, we don't really think you need a gasket for the cap, and we weren't prepared to install a gasket on our cooker for testing since, we surmised, it might be hard to get off. In addition, one poster to one of the Big Green Egg forums had asked if you could still use the ceramic cap or the DFMT with the gasket in place. Personally, we feared that forcing the DFMT or ceramic cap down over the gasket might force the edges of the gasket to peel away from the cooker and eventually the gasket would come loose. So again we were prepared to just recommend not using the gasket at all.
Then we had a brainstorm.
Unfortunately, brainstorms often don't go well, so we'll precede this next segment by saying that nowhere in the instructions for the Eggware cap do they warn you against using using your cooker at high temperatures with the cap or the gasket. Also, had we known how this would turn out, we would have definitely filmed it for your enjoyment. Alas, you'll have to be satisfied with our written account.
We decided it didn't matter if you stuck the gasket to the cooker, or if you stuck the gasket to the inside of the base of the Eggware rain cap, so we installed the gasket by attaching to the inside of the base of the cap. (We still believe this is so and don't believe that what happened was the result of attaching the gasket to the base of the cap.)
So, things were going along fine as the cooker rose to 850° and stayed there for about 30 minutes. We then decided to shut the cooker down by closing the bottom vent of the cooker and then the vent on the Eggware cap. Dark foul-smelling smoke immediately began seeping from the edges of the Eggware cap. Within no more than 1 to 1.5 seconds, black evil-looking goo started oozing and bubbling from between the cooker and the lower edge of the base. We immediately removed the cap and the base to prevent any permanent bonding between the base and the cooker and sure enough the entire gasket had virtually instantly melted. Here are photos of the remnants after things had cooled down:
So, what happened? We think that as long as the hot air from the cooker was able to shoot through the cap and out the vents, there wasn't enough heat transfer to the metal cap to melt the gasket. Once the vents were closed and the hot air was trapped, the air temperature inside the cap most likely went through the roof, heating the cap and melting the gasket. So what's the takeaway from this? Well, personally, we just don't see a need for the gasket, for a number of reasons. First, it melts. Second, if you want to use your Ceramic Cap or DFMT, you may damage the gasket. And third, we just don't see a need. It worked perfectly fine without the gasket. However, if you feel you want a gasket, Ron Pratt on the original Big Green Egg Forum is selling short sections of Rutland gasket for use instead of the gasket which comes with the cap. We'd suggest looking Ron up over there and purchasing a piece of Rutland. You can then attach it to either the cooker or the cap using Permatex Ultra Copper gasket maker.
One last observation we can make is that there appeared to be little discoloration of the stainless steel after running at such high temperatures. Below is a photo of discoloration that occurred on the base, but there was none on the cap which fits over the outside of the base and would hide this discoloration:
So other than our little mishap with the gasket melting (such is the life of a test pilot), we feel like this is a great device. We only thought of one slight improvement we'd like to see, which would be to have some markings on the cap beneath the vent with the tab, so that you could have a visual indication of how you have your vent set and how much you have moved it when you make adjustments. If you are interested in one of these Eggware Vented Chimney Caps, you can find them on the web at www.eggware.net. (Note the address is .net, not .com!)
06/23/13 UPDATE: We were contacted by the manufacturer to discuss what happened with the high temperature testing and the melting gasket. They subsequently sent us a second cap for testing that included a gasket made from a meta-aramid material. To keep things short, we'll just call it Nomex®. Here are some photos of the Nomex gasket:
The bottom edge of the gasket is aligned with the start of the flare in the sides of the Eggware cap's base. We then placed this on our medium Big Green Egg cooker and repeated our high temperature efforts where we let the cooker sit at about 900° for 30 minutes with the Eggware cap in place. We took the upper piece of the cap off after about 15 minutes in order to take the photo of the gasket in place at 800°, but then we replaced the cap and let things sit until we closed the vents and let the cooker cool off.
When we closed the vents using the original gasket, the results were instant and spectacular. The gasket melted, smoke began pouring from the cap and black bubbly oozey (oozy?) stuff bubbled out of the bottom of the cap. When we closed the vents using the Nomex gasket, we were prepared. We had our high-definition video camera running, Canon 7D digital SLR ready, and our infrared thermometer was ready in case we needed to take any temperatures. Everything was ready. We closed that vents and.....nothing happened. We allowed the cooker to cool, we took the cap off to examine the gasket and everything was fine.
So, as you can see the Nomex gasket did just fine and might be a worthy replacement for the original gasket if you plan to do any high temperature cooking such as Neopolitan pizza or searing steaks. Eggware is digesting all of this and deciding how to move forward from here. But if you happen to have a scrap of Nomex gasket lying around, you might consider using it on your Eggware top. Also, we have heard rumors that Big Green Egg is now putting some sort of gasket on their chimneys in order to keep the tops from falling off when the lid is opened. If you have one of these new Eggs, you might check to see if it is the old felt material or something better. If it is the old felt and you wish to use an Eggware cap at high temperatures, you might consider replacing it with something that can withstand the higher temperatures.
07/20/13 UPDATE: Two updates, really. First of all, Eggware has decided that the original melting gasket needed to be replaced, and indeed they have replaced a few gaskets and entire cap assemblies for some reported melted gaskets in the field. Moving forward, they will be shipping new caps with a Nomex gasket. If you have a cap already with the old gasket, you can contact them for a free replacement Nomex gasket.
Second, at the request of some customers, they have added a silicone rubber "handle" to fit over the tab on the top piece so that you can more easily grab the tab when adjusting the vents. Also, it should provide protection against heat as you grasp the tab. Of course, don't forget all the hot air that may be pouring out the vent. Here's a few photos to show this new addition: