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Glass Coffee and Espresso Mugs by Mainstream Source



16oz Double Wall Coffee Cup with Bamboo Spoons




Quality and ease of use

Our double-walled coffee and espresso mugs are lightweight and thermal, made from the same type of borosilicate glass as measuring cups and pyrex glass ovenware. Coffee stays hot, hands do not!

When you grab our Mainstream Source double-walled coffee or espresso mugs, your hands stay cool (or at room temperature!) while your beverage remains hot…or freezing if you add ice.  The mug has an outer wall and inner wall, which is aesthetically pleasing in addition to functionality.  The glass is finer than regular mugs and so it is less soluble, which means that your beverages taste cleaner and fresher because, when washed properly, they contain no residue; no leftover acid content seeps in from your previous beverages, making for a much more enjoyable experience and a longer-lasting cup.

How are you able to do this?

We use borosilicate glass to accomplish this.  This is the same type of glass used in laboratories to make vials… and in glass ovenware & industrial settings that can more easily accept extremes in temperature change.  In fact, most borosilicate glass can accept temperatures up to 340 degrees Fahrenheit.  This glass is heat and cold resistant, with a suitable temperature range between -20˚C to 150˚C (-4˚F to 302˚F), so you can theoretically hold a glass of boiling water without burning your hand.  These are thermal mugs in that context… a beverage can stay hotter longer when it starts out hotter.  These are not, however, thermal in the sense of a ‘thermos’ bottle, which is made to seal and keep beverages at hot or cold temperature for hours at a time.


This double-layer structure is aesthetically pleasing and enhances the experience and comfort of the user.  One of the many reasons we chose this product to sell is because we very much enjoy bringing these out to delight our own guests!

The double-wall creates a glass within a glass.  During production, manufacturers use one of two different methods:

    1. The air between the glasses is sucked out, which creates a vacuum.  By not allowing the heat to escape or enter, it helps to keep your beverages at the correct temperature for a longer period than normal mugs.

    1. If the middle layer is not vacuumed, the outer layer of the cup has a vent hole preventing the mug from deforming or exploding.  After manufacturing, the hole is sealed, so you will see a little plastic plug in the bottom of the outer glass on some brands.  This is not how our mugs are manufactured.  We feel that the plastic plug can deteriorate quicker and absorb outer elements over time, so we did not choose this process.

What is most glass made of?

Basically, glass is made from sand; well, liquid sand!  Most glass is fashioned from soda ash, silica (silicone dioxide) and lime.  This is usually described as soda-lime glass.  In manufacturing plants, they will use different proportions of these ingredients at a very high heat to fill a mold in order to make the glass of your choosing.

If you add other materials, you can create a different version of glassware.  For instance, stained glass contains metallic compounds added to melted glass, and most high-end crystal adds lead oxide.  When you add lead oxide, the crystal is easier to cut and can be much thinner at the rim, but recently lead has been found to be toxic in certain applications and many suppliers (including ourselves) have moved away from lead in any form in their products.

Borosilicate glass basically has a larger amount of silica than regular glass.  Boron trioxide is added to the mixture; usually around fifteen percent of borosilicate glass contains boron.

Windows and vases… in fact, most kitchen glassware is made from regular soda-lime glass.  This glass is considered more durable as long as you stay within a normal range of temperature.  This glass is more likely to break when you drop it or strike it, and it shatters when it breaks into many pieces.

Why would I choose borosilicate glass over regular glass or ceramic?

Boron and silica are entirely safe, and both are non-toxic ingredients.  Adding boron to the glass gives it the added benefit of making it less soluble, so it’s much harder for other ingredients to seep into the glass, making it even safer to drink from.  It is also made to reduce friction, which makes it dishwasher-safe.  These cups are easier to clean because of the fineness of the glass.

Adding the boron prevents the glass from expanding at a high rate like normal glassware when exposed to higher temperatures, so it generally won’t shatter under really high temperature, at least it won’t as fast as normal glass does.  When you add a higher proportion of silicone dioxide, you also make the glass more resistant to breakage… and usually when it is broken, it breaks into larger pieces and usually doesn’t shatter.  This glass goes through higher process requirements than most glass.

Also, because the ingredients of the glass are finer, it does not absorb previous tastes like most ceramic mugs.  So, if you drink a thick tea and then a light tea, for instance, you shouldn’t taste any of the previous beverages ever when washed properly between uses.

In fact, if you’re a coffee connoisseur, it matters to have a glass that is as clean and pure as possible, whenever you grind your own high-quality coffee beans, use French-press and infusion, Nespresso or even higher-end machines, or even if you are an old-school drip or percolator user, you’ll love our mugs!  Whether you wake up to piping-hot coffee or shockingly cold iced coffee, you’ll be delighted with our Mainstream Source double-walled coffee or espresso mugs!

Features of our coffee mugs and espresso cups

Our double-walled mugs are made from food-grade standard glass, built to withstand acid corrosion, which can occur in ceramic and regular glass mugs.  For this reason, it’s great with carbonated beverages, drinks that contain fruit acid, green tea, black tea, coffee, espresso and virtually any of your favorite beverages.

    1. Shock-resistant at higher temperatures than normal glass

    1. Heat and cold resistant

    1. Entirely safe and non-toxic

    1. Lighter than ceramic mugs

    1. Durable and shatter-resistant

    1. Excellent quality

    1. Better for the environment, eco-friendly, non-toxic

    1. Does not absorb other tastes easily.

Why should I choose Mainstream Source double-walled mugs over another brand?

At Mainstream Source we put a little extra care into all of our products to ensure that the quality is higher than almost all of our competitors.  When we created the mold for our double-walled mugs, we made the glass just slightly thicker and the handles more durable than most other brands, so you can be assured that you have a high-quality, lasting, durable, eco-friendly mug that you will enjoy hopefully for many years.

What happens if I have any problems?

Mainstream Source unconditionally guarantees all of our products, so if you have any issues whatsoever, just contact us at and we will resolve your issue to your satisfaction.

Different methods of brewing coffee at home

Most of us go for ease in accessing a fresh cup of coffee in these busy times.  Keurig, Cuisinart and other top brands offer the ‘pod’ style single-cup coffee, which has become actually more palatable with the newer machines, even for discerning tasters.  Automatic coffee machines are the most common household option, and some higher-end brands offer machines that will grind your beans fresh on a timer and have a steaming cup ready for you each morning.  These options are excellent for any coffee drinker, but there are many other ways to bring out the taste of the beans for a more gourmet experience.

Coffee Cone Drip/Pour

Using a cone and paper to hold the ground beans, and pouring your hot water over the beans, as it drips slowly into the pot.  Depending upon the materials of the cone (Cones come in plastic, ceramic, glass and stainless steel), your coffee may taste cleaner and fresher and bring out more of the natural flavor in the bean.  This method works great with organic beans as well.  Grind your beans a bit coarser, at about medium-fine, and use three tablespoons of coffee (about 21-22g).  Glass cones may be the best option for the cleanest taste.  This method is portable, makes a single cup of great coffee, and all you need is the cone, pot and paper filter to match the cone.  A friend recalled a camping trip where they brought everything but the paper filter, and they were able to use a paper towel as a filter, which worked surprisingly well in a pinch!

You can also purchase a Chemex flask in various sizes, which works in the same way, uses a thicker filter and can brew 4 to 6 cups or more, depending upon the size.  This is a bit more expensive but extremely rewarding.  It’s a bit more fragile, requires a brush for cleaning, and it’s also harder to clean than the standard drip cone/pot/filter.

•Percolator (Stovetop or electric)

If you’re a baby boomer (and if your parents were coffee drinkers), you will remember the familiar, repetitive sound of coffee being pushed up through the percolator every morning.

Although this process of making coffee was hugely popular immediately after being invented in 1933, it still remains popular in many parts of the world.  Water is boiled in a metal pot.  The steam pressure from the boiled water in the lower chamber passes through fine to course ground coffee, placed into the mid-chamber of the pot.  The brewed coffee is held in the upper chamber throughout the percolation process.  The key to this process is steaming pressure, and the better the pressure, the better the coffee.  The whole process usually takes between 5-10 minutes.  Most coffee made in this fashion tends to be on the bitter side but strong and vibrant.  Depending upon the size of the percolator, up to 12 cups can be made at a time, using 2-3 tablespoons (16-22g) of coffee per cup, and it’s not terribly hard to clean.


French-Press coffee making has been around now for a century.  Many coffee connoisseurs swear that this is the easiest, best way to brew amazing, consistent coffee.   First, superior coffee beans are chosen and course-ground.  2 or 3 tablespoons of coffee (around 16-22g) are allotted for one cup depending upon desired strength (and, depending upon the size of your press, you can make up to 8 cups at once).  The ground coffee is first soaked, steeped and strained in a press pot in hot water, bringing out flavor from the beans essential oils, diffusing and preserving antioxidants and caffeine for a pure, super-tasty cup.  This process is much easier to clean than the Chemex process.

Another version of this is the AeroPress plunger-press method.  At the bottom of the brew chamber, a filter is placed into a coffee basket.  2 to 3 tablespoons of fine to medium coffee grounds (16-22g) are placed into the chamber, hot water is added and the coffee steeps for a period of time.  Then, you press down a plunger, which creates air pressure, forcing the steeped coffee through the filter, into your cup.  Generally, this process makes one cup at a time and it’s portable. This process is somewhat easier to clean than the Chemex process, but not as easy as French press.

If you’re looking for a complex but unbelievably rewarding, fully flavorful experience, either of these methods is for you.

•Siphon/Vacuum method

This process has been around since the mid-1800’s.  A 2-vessel coffeemaker is needed.  Medium to course coffee grounds are added to the upper chamber, and steam-vapor pressure forces the boiling water up, immersing the coffee.  When the coffee maker is removed from the heat, the brewed coffee then drips through a filter into the bottom vessel, making a delicate, mellow cup of coffee.  Usually, 6-7 tablespoons of coffee (40-48g) are used and the process takes around 6-7 minutes to complete. Unfortunately, it’s hard to clean, not portable and delicate.  In the 1800’s a candle was used to heat the water, but now campers can use a butane burner or you can plug it in!  It requires a cloth or metal filter.

Tips and Tricks for Great Coffee:

•The best coffee comes from pure, filtered water.  Starting with cold or room temperature water can improve the process.

•Always use the freshest roasted beans available, and grind them immediately before making your coffee!

•Always feel free to adjust the amount or type coffee you add.  Everyone’s tastes are different, and one may prefer a strong, robust cup or a smoother, delicate blend.

•When using paper coffee filters, purchase unbleached (usually brown in color) filters or rinse the bleached white filters in hot water before using them to remove any chemicals from the bleaching process.

•Unless you’re percolating, hot water should be just short of boiling temperature (96˚C or 205˚F).

•When pouring coffee during a drip method, pour slowly and methodically over all of the ground beans in order to saturate the coffee grounds for premium extraction.  If you can find a narrow-spout pouring apparatus, this will work even better.

•If you rinse your coffeemaker with hot water prior to brewing (and you can also rinse the cup in hot water if the temperature is very cold), your coffee will start out hotter and taste better.

•Coffee grounds work great for composting!   Be careful, though, because a common idea is to pour the coffee grounds directly into the soil around plants, and this can cause mold in some instances.


Most coffee drinks can be served hot or iced, depending upon your preference.

ESPRESSO was originally conceived in Italy.  It is basically very strong, concentrated coffee.  The espresso method uses very finely ground beans along with high water pressure to make a very strong shot for a quick pick-me-up.  Experiment with a different variety of beans and also the degree of roasting, for new tastes.  DOPPIO is basically a double-shot of espresso. RISTRETTO is basically a pulled, short espresso, even more concentrated. LUNGO is a long-pulled espresso.
CAPPUCCINO, also with its origins in Italy, begins with espresso and adds steamed foamed milk.  In essence, the steamed milk is topped with a light layer of foam. You can also substitute skim milk, almond, soy or oat milk and try flavoring with caramel or cinnamon.  Adding chocolate turns it into a MOCHA.

LATTE is very similar to a cappuccino but instead of layering, the steamed milk and foam are mixed together.  Favorite latte recipes add Vanilla or Chocolate, and like cappuccino many non-dairy or skim milk combinations can be used.  Another version of this is a GALAO which basically combines lots of foamed milk with a little espresso.

CORTADO resembles a cappuccino in that it is layered, but it does not include the foam, so most Cortado drinks contain equal espresso and steamed milk.  Vanilla is a great flavor for this, and if you add chocolate it almost tastes like a super-charged hot chocolate!  Another name for this is a FLAT WHITE.  A less potent but equally pleasing version of this substitutes the espresso for coffee, adding steamed milk, in order to make a CAFÉ AU LAIT.

MACCHIATO also resembles a cappuccino, but it does not include steamed milk, only a layer of espresso and foam.  Our favorite is Caramel Macchiato, but during the holidays you’ll see many different flavors.

AMERICANO is simply espresso with hot water added, which basically turns it into a cup of regular coffee!  Substitute the water with coffee, adding espresso, you’ve turned this drink into a RED EYE

Finally, why not make espresso into a dessert?  Adding ice cream turns an ordinary espresso into an AFFOGATO .

T Green Phantasm
Reviewed in the United States on January 18, 2023
Size: 5.5 oz Espresso Mugs

We like the size–fairly small—and the look—classically simple.
We’ve only had them a week, but they do seem to keep our coffee a little hotter, and that’s why we bought them. So we’re pleased. And they’re reasonably priced, too.

Reviewed in the United States on October 12, 2022
Size: 13.5 oz Coffee Mugs

These mugs are just nice! They do what they’re supposed to do which is to contain your beverage and keep it warm and unlike your basic coffee mug, the outside is separate so you won’t burn your hand. They are also very modern looking and a conversation piece. Great design and will make for a nice gift!

Reviewed in the United States on October 29, 2022
Size: 13.5 oz Coffee Mugs

These double walled glasses are great! Not only is their size perfect for a variety of teas and coffees, they are also super cute and lightweight. Their double wall prevents you from handling a hot cup of tea/coffee and getting burned which is an absolute plus especially with young children in the house.

These are a great addition to your house for you and your partner. And the wooden spoons that come with them are super cute.

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