“The quality of the product that deck ovens produce was the bottom line in why we wanted to get them,” Rick Robbins says. “Still, there are a lot of other incentives, including fuel savings and control of the baking.”
For the volume of artisan bread being produced at Pittsfield Rye, Robbins says that he couldn't beat a deck oven. Not every variety of deck oven is created equal, though. Ovens and their peripheral loaders are a major expense, so do your research. The ovens use three main heating methods, and each has advantages and drawbacks that predispose them to different applications. For bakers considering adding deck ovens to their operation, an understanding of the three primary varieties — cyclothermic, steam tube and thermal-oil — is essential for determining which will be the best fit.
Michael Eggebrecht, a consultant with Artisan Baking Resources in Stevenson, Wash., has studied the differences among the ovens. The method of getting the heat into the baking chamber is what differentiates the ovens. “I arrived at the fact that for artisan bread, there is a type of deck oven heating system for each application,” he says. “It largely depends on what you're going to use your oven for and what you want from your product.”
The cyclothermic oven, which uses air to move heat into the baking chamber, is an old and simple technology that is popular in Germany and Eastern Europe. Heat produced by combustion yields to the product on the deck in the baking chamber by way of air cycling through tubes or panels placed above and below the baking chamber.
An electric convection fan, located at the back of the oven, drives the hot air circulation. The ability to constantly recycle the heated air aids in keeping fuel consumption low. Ovens using this heating method have less mass than steam tube or thermal-oil ovens, so cyclothermic ovens need to use more energy and be preheated to a temperature higher than the actual baking temperature.
Cyclothermic oven-produced bread tends to have a large volume and a thin crust thanks to strong oven spring characteristics. The temperature drop at loading and subsequent recovery to baking temperature slightly delays crust formation. Eggebrecht says that versatility is the best characteristic of the cyclothermic oven. The temperature control allows bakers to use a baking curve and to adjust the temperature throughout the day.
In a steam tube oven, tubes filled partially with water are placed above and below the baking surface. They run to a combustion chamber made of fire-resistant bricks beneath the oven. There, a burner heats the tubes, causing the trapped water to turn into steam that naturally circulates through the tubes into the oven. After releasing its heat, the steam condenses back to water and flows to the combustion chamber to be reheated.
Steam tube ovens tend to produce a drier bake than cyclothermic ovens, Eggebrecht says. The large surface area of exposed, superheated tubes in the baking chamber has a drying effect on the baking environment. This causes crust to form more quickly and oven spring to be comparatively diminished, so bread may exhibit smaller volume and thicker crust. The large thermal masses of steam tube ovens precipitate a better recovery time than cyclothermic ovens, providing a consistent temperature throughout a bake cycle.
Thermal-oil deck ovens consist of two parts: the oven itself and a remote boiler. Oil is heated in the boiler and piped to the oven similar to the system in a steam tube oven. After the oil passes through the heating chamber and the heat is radiated, the oil returns to the boiler to be reheated.
Oil is a better conductor of heat than water, and combined with the considerable thermal mass, thermal-oil ovens possess the fastest recovery time of all deck ovens. These ovens are extremely energy efficient, Eggebrecht says, as one boiler can be used to heat a number of ovens. The oil requires pumps and controls that are non-existent in the steam tube oven, which increases the cost and complexity of the oven. Larger bakeries may even require a technician to be on hand to maintain the oven.
The fast recovery time gives the thermal-oil oven a consistent, even bake. The bread has comparable characteristics to the steam tube ovens. The ovens have less flexibility in temperature changes than steam tube ovens, and are not conducive to building temperature curves into the baking time.
“There are lots of things to think about when looking into those three ovens styles; you have to identify your products and your baking times,” Eggebrecht says. “A baker has to compile a list of products, baking times and temperatures, and must factor in variables like par-baking and how much product fits on a deck. A thorough analysis tells you what system best fits your particular bakery. You have to be especially thorough when you take the loader into consideration, because there is a lot of timing that goes into it, and you can't unload anything before you've finished loading.”
Loaders vary in automation and cost. The price alone can be intimidating, but the fact remains that bakers need a way to get product into and out of the oven, and that can be the most labor intensive of bakery tasks. Robbins says when looking at loaders, it all boils down to volume and labor.
“You have to look at where you are in terms of production volume, and think about where you want to be. Basically, it's a cost/benefit analysis,” he says. “How much does labor cost now, and how much would it cost if you grew a little bit; would automation cut down labor enough to justify the increased cost? With deck ovens, you don't really need to turn product, so most of the labor is in the loading and unloading.”
Some artisan bread bakers doubted the benefits of oven loaders over traditiaonal peels. They feared quality would be sacrificed to convenience, and that increased automation would only add another degree of separation between a baker and his or her bread. The perception still exists, but oven loaders can actually improve bread handling.
“Typically, we are seeing that oven loaders can handle bread better than a human can,” Eggebrecht says. “Imagine a fully risen piece of ciabatta. Would you rather handle it by hand or use an automatic loader with a seamless transfer? If you're looking to automate, and you are concerned about product quality, loaders are a good place to look.”
As is true with all new equipment, bakers can rely on other experienced bakers for advice when purchasing deck ovens. Set up appointments to watch the deck ovens in action at real bakeries, particularly bakeries with similar production schedules, methods and product lines. Better yet, try them out yourself.
Robbins, as a rule, takes notice of the bigger equipment items in every bakery he visits. While visiting other bakeries looking at silos, he also was keeping a close eye on the ovens in those bakeries. After a few years of seeing deck ovens in action, Robbins decided it was time to get more serious about them.
“Through the sales rep for the oven company, we set up a visit to another bakery using the model we were looking at. They basically gave us carte blanche to try everything out and actually use the equipment,” Robbins says. “They had an older, remodeled oven, too, and were using both. We could see the products side by side, and we could really see the difference; where one oven excelled and the other didn't.”
Robbins expected some improvement in energey efficiency with the new ovens. Other bakers told him to look for a nearly fifty percent savings on the gas bill, which was an unexpected incentive. Armed with an understanding of oven varieties and the advice of other bakers, Robbins was able to determine which deck ovens fit his bakery and his product line.