Materials Matter
While plastic has some benefits, its our opinion that it shouldn't be used as a pet bowl. Many plastics contain chemicals that, if ingested, are thought to mimic hormones in mammals and could cause an array of negative health effects. Most plastics are also micro-porous, meaning no matter how often or how well you clean them, bacteria can build up over time, leading to muzzle irritation and chin acne in pets. There are applications where plastic makes sense, but it's just not pet bowls.
Ceramic can make a fine option for pet bowls, but its important to ensure you're getting a high quality ceramic bowl upfront and to monitor it for chips or cracks over time. Some ceramic glazes contain the heavy metal lead, so be sure any ceramic pet bowl you're considering is made with a lead-free glaze. Also, the glaze is very important to the proper function of ceramic, particularly when used in a food or water setting. The glaze is what makes ceramic hygenic. Even small cracks or chips in the glaze will expose the pourus ceramic underneath and compromise your ability to properly clean the bowl.
Stainless steel presents the best combination of properties for pet bowls. Its hygenic, meaning the surface won't harbor bacteria and can be readily cleaned with soap and water washings. It's also very durable. Most damage that can occur with stainless steel will be cosmetic (faint scratches, stains, minor dings, etc.). But not all stainless steel is created equal...
Stainless Steel Buying Guide
Did you know that there are 100's of different grades of stainless steel? While no grade of stainless steel is inherently bad, they are intended for different applications. Some grades make great mufflers or appliance fronts, but not all grades make great pet bowls.
Know Your Grade
There are simply too many grades of stainless steel to discuss them all, but the most popular grades that are widely accepted as food contact safe are 200 and 300 series stainless steel. The 200 series stainless steels were designed to be a lower cost alternative to the 300 series and may not hold up as well over time.
Check Quality Standards
In the past, some pet bowls have been recalled for being radioactive and others have been found to contain high levels of lead. These things can happen when there aren't sufficient quality standards in place. So look for products from companies that carefully source their raw materials, and even better, that perform testing on their finished products to further reduce risk.
Be Curious
There are a number of things that can tip off an attentive consumer to low quality products. Things like specifying 'stainless steel' without listing a grade, 'hand wash only' instructions, and 'for pet use only' labels could be indicative of a low quality product.