The Best Kilns for Bottle Slumping

The cubist painter Amédée Ozenfant once said, “Art is the demonstration that the ordinary is extraordinary.” Nothing could be truer when it comes to bottle slumping, renowned for recycling mundane vessels and turning them into fun, functional art.

If you’re a bottle slumping enthusiast, or would like to become one, purchasing a kiln is an important first step. There are many aspects to consider if you’re interested in investing in a kiln for bottle slumping, either at home or in a studio, so to make the process less overwhelming, we’ve put together a guide addressing the most important things you’ll want to take into account.

At the end, we’ve also included our recommendations so that you can find the kiln that best fits your needs and interests.

Requirements for a Kiln for Bottle Slumping

When thinking about buying a kiln, it’s important to consider both what you’ll be creating and the space in which you’ll be creating. Here are some of the most important questions to keep in mind:

What sized bottles are you slumping and how many?

Every time you fire, you will want to be able to fill your kiln to maximize efficiency, so to determine the size of the kiln you should buy, consider not only the dimensions of the pieces you’ll be making, but how many. Unfortunately, since many bottles are long, they will not fit in many smaller kilns.

What kind of space will you house the kiln in?

Other important dimensions to consider relate to the studio, room, or garage space you’ll be dedicating to your art. Before deciding on a kiln size and model, know the maximum length, width, and height you’re willing to accommodate for, and don’t forget that a glass kiln needs to be a minimum of 12 inches away from any walls, and a ceramic kiln needs to be at least 24 inches away from any walls.

Additionally, be sure to think about what kind of ventilation the space has and what kind of access to breakers and outlets are available.

Do you plan on using your kiln for additional projects?

If you’d like to use your kiln for firing ceramics or glass fusing projects in addition to bottle slumping, you’ll have to consider how this will affect the type, maximum temperature, and programming abilities of the kiln you’ll need. Consider all other materials, glazes, and firing procedures you’d like to work with before deciding on a kiln.

How much power do you have available?

The bigger the kiln, the more energy is required to run it, so try to match the voltage and amperage requirements of your desired kiln to what you have available in the space you’ll be housing it. If you decide on a kiln that has higher energy requirements, be prepared to make further investments in its installation.

Factors to Consider When Buying a Kiln for Bottle Slumping

When sifting through the vast number and variety of kilns offered, it’s useful to have a list of specific qualities and characteristics you want your kiln to have. Here is an overview of attributes to consider when searching for your perfect match:

Temperature

Though different glasses have different viscosities and will therefore vary in the time it takes them to be slumped, you won’t ever need to fire at a temperature higher than 1500 degrees Fahrenheit. However, if you intend to use your kiln for projects other than bottle slumping, you might want to consider kilns with higher maximum temperatures.

Glass fusing projects can be fired up to 1700℉, low-fire clay ranges from 1850-2135℉, mid-fire clay between 2160 and 2290℉, and high-fire clay up to 2380℉.

Additionally, it is important to buy a kiln that exceeds the maximum temperature needed for your work. Over time, a kiln´s power is reduced, meaning its ability to hold a high temperature decreases.

Therefore, after you have decided the minimum temperatures needed for your projects, overestimate the temperature by 200-300 degrees fahrenheit.

Visibility

Due to the unpredictable nature of slumping different kinds of bottles with unknown glass viscosities, you must be able to see the glass as it bends during firing.

Of course you can simply open your kiln and look in, but if you have a toploader, the blast of heat straight to the face can be unpleasant at best, dangerous at worst. Therefore, front-loading and clamshell kilns are easier to use when slumping bottles.

Another option is to purchase a kiln with peepholes, allowing you to position your work so as to easily look in without letting out a significant amount of heat.

Glass Kilns vs Ceramics Kilns

Deciding between using a glass kiln and a ceramics kiln depends largely on what other projects you plan on making besides slumped bottles.

Because it is a low-fire material, and due to its flat nature, even heat distribution is extremely important for fused glass firing. Ceramics kilns typically only have side elements, while glass kilns insure that heat radiates not only from the sides, but from the top of the kiln as well. This helps counter glass’ sensitivity to temperature variation. Therefore, if you are planning on doing other glass work, or only slumping bottles, a glass kiln is your best choice. However, bottles can typically also be fired in ceramics kilns, which can easily achieve the temperatures required for slumping while also firing clay projects.

Depending on the maximum temperature the kiln can reach, ceramics kilns can be used for low-fire materials like glass and earthenware, mid-fire stoneware, high-fire stoneware, and porcelain, which requires the highest temperature levels.

If you are a jack-of-all-trades who would like to dabble in both glass and clay, there are also some kiln models designed specifically to fire both glass and ceramics projects, so this might be a worthy investment for you.

Size

Kilns range significantly in size, and the best fit for you will depend on the type of bottles you’re firing, how many, and how big your studio space is.

Keep in mind that small, 12 oz bottles are typically around 7” long, while wine bottles may be up to 13” long. When used for bottle slumping, many smaller kilns (up to 9” x 11”) are incapable of firing more than one piece, but can be great for test items.

A kiln ranging in size from the aforementioned dimensions to 18” x 18” is perfect for those who are interested in creating no more than two or three pieces at a time.

A 23” x 27” kiln is a common purchasing size for average glass artists creating a number of pieces, potentially along with fused pieces, other slumping projects, or ceramics, while anything larger than a 29” x 27” kiln is best for large production use.

In general, larger kilns take longer to heat up and cool down, and larger kilns will require you to lengthen your hold time on your target temperature during slumping, so while they may be more practical for larger bottles, you will be able to fire more projects per day with a smaller kiln.

Price

Soul Ceramics guarantees the lowest prices available, with glass and ceramics kilns ranging from just over $300 to close to $6,000.

Within the under $500 price range, Soul Ceramics offers the Jen-Ken GS-Fuse Box Glass Kiln for $322.99 and the AIM Kilns 64K Electric Ceramic Kiln for $309.99. Both of these are small, table-top kilns ideal for test pieces.

On the other end of the spectrum are kilns like the Jen-Ken AF Oval 31” 3” Ceramic Kiln for $3,559.99 and the Evenheat Glass Kiln Studio Pro 41 for $3,689.99 . These kilns are capable of firing the biggest pieces in a studio, come equipped with many special features, and are intended for very prolific artists or communal use.

Between the extremes are dozens of other kilns, ranging in both size and price. As a general rule, the bigger the kiln, the higher the price, but price also depends on a kiln’s capabilities and versatility.

Electricity and Voltage Requirements

Voltage and amps are two important elements to factor into your kiln decision as well. The voltage of a normal household is 120V. For smaller kilns, this should not be a problem. However, larger kilns often require 240V; if you are interested in installing this kind of kiln in your home, you might want to consult an electrician.

Additionally, you will need to be certain you have a breaker that meets the amperage requirements for your kiln. First, determine how many amps you have available - look in the fuse/breaker box of the plug you want to use to see what number is indicated. Most U.S. homes are protected by 15-20 amp breakers, but a large kiln may require 40. Even if you have the correct voltage for a larger kiln, the kiln won’t work if the amp number is not high enough.

In general, the larger the kiln, the larger the energy requirements, thus providing another motive for beginners to start with a kiln smaller in size.

Location

Considering location is important not only for the size kiln you purchase and electricity available; it can also determine the necessity of certain kiln attributes. Mainly, if your kiln is going to be in a place that is frequently populated, like a studio, you’ll need to heavily consider ventilation needs. Make sure your kiln is near a window, and look at models with good venting systems.

However, if your kiln is going to be in a garage or shed, where there aren’t a lot of people, you don’t need to worry about purchasing a kiln with an excellent venting system.

Controller Type

All Soul Ceramics kilns come with a control, but most models offer you the choice of different types.

The most basic, elementary kilns come with a manual control, which requires you to start the kiln at the lowest setting and be responsible for all changes in temperature throughout the rest of the process. While this kind of control does require more effort, it also allows you the most power to regulate the firing process.

Electric controls are more expensive, but they are easier to operate, due to their ability to regulate temperatures independently. These range from the Set-Pro Control, a three-button system that lets you choose between 4 different firing programs, to the TAP Control, a touchscreen device that allows you to create your own personal firing program, chose one of many pre-programed options, or use its wifi connection to develop and edit programs from a computer, tablet, or phone.

For bottle slumping, a manual controller can allow you to experiment more directly to determine what temperatures and firing profiles to use based on the bottles you’re slumping.

However, for beginners, an electric controller will help you to feel less like you are taking a shot in the dark with temperatures, and may even have specific bottle slumping settings. Also, an electric control is a good investment if you’re going to be doing a variety of firings, since reprogramming is a nuisance. More detailed descriptions of specific controls we offer can be found here.

Accessories

It’s a good idea to consider ordering accessories with your kiln so as to minimize shipping charges. For bottle slumping in particular, here are a few important things to consider investing in:

  • Slumping molds: While slumping molds are unnecessary if you’d like a completely flat end product, they can make the piece more interesting or useful. For instance, molds are essential if you’d like to create a cheese tray with a raised handle or a dip holder. Molds come in many different shapes and sizes.

  • Kiln wash: If you aren’t buying a glass kiln with fiber shelves (which require kiln paper for lining), kiln wash is essential to ensure that your glass bottles don’t fuse to the shelf or any molds you may be using. Different types of wash exist for firing at different temperatures. While you can make your own kiln wash, it is easier and less risky to buy it instead.

  • Kiln shelves: The benefit of using kiln shelves, as opposed to firing directly on the floor of your kiln, is that then the texture of the kiln floor won’t transfer onto the pieces you’re making; kiln shelves provide you a flat, untextured surface to fire on. Additionally, if you have an accident, kiln shelves can create a layer of protection between the hot glass and the floor bricks, which could be seriously damaged from the material.

  • Kiln posts: Kiln posts elevate shelves from the floor of the kiln and provide support while optimizing space within the kiln for firing. They are available to order in many different levels of thickness and height.

  • Bricks: Used as an insulator by lining the inside of a kiln, bricks come in a variety of shapes and two main materials. Hard bricks are strong and dense, and are great for structural support. Soft bricks are less capable of withstanding high temperatures, but retain heat more effectively.

  • Furniture kits: Instead of puzzling over what kinds of shelves, posts, bricks, or wash you need, one easy option is to invest in a furniture kit, which can be purchased automatically with many kilns offered from Soul Ceramics. Kiln furniture kits are an easy way to acquire the most essential accessories in a single purchase.

Our Recommendations for the Best Bottle Slumping Kilns

After considering your needs and taking note of the attributes you’re looking for in a kiln, it’s time to consider some different models. Taking into account all of the important attributes that contribute to a kiln best suited for bottle slumping, here’s the list we’ve compiled of the top 5 models we feel are a good fit for home studios:

Jen-Ken AF3P-Bonnie Glo Tall Glass Kiln

  • Size: 15” x 9.” This is a good size for those wanting to try bottle slumping, as it is small enough only for one or two pieces at a time. It’s also great for test items as well as any other smaller fused glass pieces you may be interested in making.

  • Price: $849.99. This kiln is reasonably priced for its size, and fits the budget of an artist trying out bottle slumping on their own for the first time or wishing to add to their studio.

  • Energy required: 120 volts, 15 amps. This kiln can be used with a standard home outlet, making it a perfect and easy fit for any garage or home studio.

  • Maximum temperature: 1700℉. This kiln will easily be able to fire any and all glass projects you wish to create, from slumped bottles to fused pieces and jewelry.

  • Additional information: The Jen-Ken AF3P-Bonnie Glo is a fast firing kiln that’ll allow you to easily fire more than once in a day. This is largely due to being made of fiber, which is another bonus since it means you won’t need to use kiln wash on the shelves when slumping bottles. Additionally, it has peepholes, allowing you to easily check to see when your bottle slumps. Due to its convenient size, low energy requirements, and reasonable temperature range, this kiln is perfect for those wishing to experiment with bottle slumping or make only a few pieces at a time.

Jen-Ken AFG ProFusion 26 Glass Kiln

  • Size: 26” x 26” x 12.” This is an average size kiln, excellent for creating a number of slumped bottles at once along with any other glass pieces you’d like to make.

  • Price: $2,689.99. Though the most expensive kiln we recommend for bottle slumping, the Jen-Ken AFG ProFusion 26 is a worthwhile investment due to its increased capabilities and space.

  • Energy required: 240 volts, 36 amps. A potential drawback of this model is that you may have to install a new breaker. Due to the 240 voltage and high amp requirement, some additional work and costs might need to go into this kiln’s installation. This model might be a good fit for you if you already are operating a studio which can accommodate high voltage.

  • Maximum temperature: 1700℉. Like the AF3P-Bonnie Glo, this kiln is intended for glass firings, and easily accommodates for projects ranging from slumped bottles to fused pieces and jewelry.

  • Additional Information: This clamshell-style kiln is also made of fiber and is known for fast firings, allowing you to do multiple firings in a day. This is useful for bottle slumping, where the many tests required can take up valuable time in a slower kiln. This kiln is accompanied by a 12-key digital controller and a two-year warranty, and is a fantastic kiln for an artist ready to kickoff a thriving bottle slumping studio.

Evenheat Glass Kiln GTS 2541-13 with Dyna Lift

  • Size: 41” x 25.5” x13.5.” This kiln is a massive, oval-shaped kiln that will allow you to slump as many bottles as your heart desires, as well as other large glass pieces.

  • Price: $2,274.99. Slightly less expensive than the Jen-Ken AFG ProFusion 26 but still a significant investment, the Evenheat GTS 2541-13 is worth the cost for its incredible size and design.

  • Energy required: 240 volts, 40 amps. Like the Jen-Ken AFG ProFusion 26, the Evenheat GTS 2541-13 is best suited for an established studio where higher voltage and amps have already been accommodated. However, if you are willing to install a new breaker in your home, this kiln could be a good fit.

  • Maximum temperature: 1800℉. Like the two aforementioned kilns, this too is a glass kiln, perfectly capable of firing all glass projects, but likely not able to accommodate clay creations.  

  • Additional information: The Evenheat GTS 2541-13 comes equipped with one of four digital controllers (your choice) for accurate operation, as well as a full stainless jacket, swing view adjustable viewing, and corner mounted hardware. This kiln is practical and durable, and comes with a two-year warranty, so is a great kiln for an artist that will be slumping for years and years to come.

We hope this guide has armed you with some important facts, heightened confidence, and good options to chose from. If you have any additional questions, please don’t hesitate to contact us, and best of luck!