Let it Flow: How to Calculate Viscosity

Viscosity is the measure of a material’s resistance to motion under an applied force. There are several formulas and equations to calculate viscosity, the most common of which is Viscosity = (2 x (ball density – liquid density) x g x a^2) ÷ (9 x v), where g = acceleration due to gravity = 9.8 m/s^2, a = radius of ball bearing, and v = velocity of ball bearing through liquid.

If you want determine viscosity in a liquid, try a simple science experiment by measuring the speed of a metal ball dropped in a container of liquid. The velocity of the ball, combined with the relative densities of the ball and the liquid, can be used to calculate the viscosity of liquids. But you can’t calculate viscosity unless you know what it is and why it’s important.

Definition of Viscosity

The definition of viscosity is “the quantity that describes a fluid’s resistance to flow. Fluids resist the relative motion of immersed objects through them as well as to the motion of layers with differing velocities within them.” Knowing how thick your material is can have huge impact on your ability to get work done. Material such as honey or glue tend to be thicker and are described as having a higher viscosity, whereas water and glycol are less viscous and flow faster.

Temperature also plays a critical role in the viscousness of a liquid. Generally speaking, the warmer a liquid is, the lower its  viscosity is and the easier it flows. The colder it is, the more sludge-like it becomes and has a higher viscosity. Understanding how to calculate viscosity can be helpful when deciding if your material is ready to use or not. So how do you determine the viscosity?

calculate viscosity

Try This Out

Calculating the Density of the Ball

  1. Measure the mass of your ball, using your balance. For instance, suppose the mass of the ball is 0.1 kilograms (kg).
  2. Find the radius of the ball by first measuring the diameter (distance of a straight line through the ball at the widest part). Divide the diameter by 2; this gives the radius of your ball.
  3. Calculate the volume of the ball by plugging the radius into the equation for the volume of a sphere. Suppose the ball bearing has a radius of 0.01 meter (m). The volume would be:  Volume = 4/3 x pi x (0.01 m) ^3 = 0.00000419 m^3
  4. Calculate the density of the ball by dividing its mass by its volume. The density of the ball in the example would be:  Density = 0.1 kg ÷ 0.00000419 m^3 = 23,866 kg/m^3


Calculating the Density of the Liquid

  1. Measure the mass of your graduated cylinder when it is empty. Then measure the mass of your graduated cylinder with 100 millilters (mL) of liquid in it. Suppose the empty cylinder had a mass of 0.2 kg, and with fluid its mass was 0.45 kg.
  2. Determine the mass of the fluid by subtracting the mass of the empty cylinder from the mass of the cylinder with the fluid. In the example:  Mass of liquid = 0.45 kg – 0.2 kg = 0.25 kg
  3. Determine the density of the fluid by dividing its mass by its volume. Example:  Density of fluid = 0.25 kg ÷ 100 mL = 0.0025 kg/mL = 0.0025 kg/cm^3 = 2,500 kg/m^3*
  4. 1 mL is equal to 1 cm^3 *1 million cubic centimeters equal 1 cubic meter


Calculate Viscosity of Liquid

  1. Fill your tall graduated cylinder with the liquid to be tested so it is about 2 cm from the top of the cylinder. Use your marker to make a mark 2 cm below the surface of the liquid. Mark another line 2 cm from the bottom of the cylinder.
  2. Measure the distance between the two marks on the graduated cylinder. Suppose that the distance is 0.3 m.
  3. Let the ball go on the surface of the liquid and use your stopwatch to time how long it takes for the ball to fall from the first mark to the second mark. Suppose it took the ball 6 seconds to fall the distance.
  4. Calculate the velocity of the falling ball by dividing the distance it fell by the time it took. In the example:  Velocity = 0.3 m ÷ 6 s = 0.05 m/s


Calculate viscosity of liquid from the data you have collected:

  1. Viscosity = (2 x (ball density – liquid density) x g x a^2) ÷ (9 x v), where g = acceleration due to gravity = 9.8 m/s^2, a = radius of ball bearing, and v = velocity of ball bearing through liquid.
  2. Plug your measurements into the equation to calculate the viscosity of the liquid. For the example, the calculation would look like this:  Viscosity = (2 x (23,866 – 2,500) x 9.8 x 0.01^2) ÷ (9 x 0.05) = 93.1 pascal seconds.


Viscosity Calculation Formula:

viscosity = shear stress / shear rate

The result is typically expressed in centipoise (cP), which is the equivalent of 1 mPa s (millipascal second).


Powerblanket Solutions

Powerblanket makes it easy to lower the viscosity of many industrial fluids by heating the container evenly to the desired temperature, allowing your material to achieve the preferred viscousness for use. This saves you time and money, getting back to work instead of waiting for external temperatures to naturally warm up your material.

Powerblanket offers various ready-to-ship viscosity products, from bucket and drum heaters to IBC tote heaters. We can also produce custom solutions for most applications. If you need better flowing fluids, Powerblanket has you covered.



Predicting the Weather

The Fine Art of Inaccuracy:  Predicting the Weather

I wake up, rouse my children for school, then check the weather.  The weather app on my iphone helps me make a lot of decisions about my day and week ahead–especially what kind of outerwear my kiddos need before they walk out the door.  My husband checks out the local forecast online when he gets to work. Some people watch the news while other obsess over what the weather channel has going on. However you get your information, there are numerous methods for coming to similar weather conclusions.

You may criticize the weather man’s accuracy, but he has already recognized his limitations.  Weather forecasters accept the fact that they cannot be perfect. Even with all of the resources available to them, they respect the fact that they are but mere mortals attempting to predict something as dynamic as the earth’s ever-changing weather.  Meteorologist rely on data from satellites, ships, airplanes, weather stations, buoys, and devices dropped from weather balloons, along with their experience, local trends, and history. And according to Nate Silver who wrote “The Weatherman is not a Moron” in the NY Times Magazine, “The one area in which our predictions are making extraordinary progress, however, is perhaps the most unlikely field, [weather forecasting].”

How do meteorologists forecast the weather?

Meteorologists and climatologists use several methods for predicting the weather:

  1. Climatology
  2. Analog
  3. Numerical Weather Prediction



Climatology is a simple forecasting method that takes data/statistics collected over an extended period and then averages the results.  Meteorologists predict the weather for a specific day and location based on the weather conditions for that same day for several years in the past.

A forecaster could examine the averages for Halloween in Utah, for example, to predict the weather for the upcoming Halloween. The climatology method works when weather patterns remain in place, but in situations where outside factors change the weather frequently, the climatology method is not the best choice for predicting the weather, as it will more than likely not be accurate.


An analog is a thing seen as comparable to another thing.  The Analog Method is a slightly more complicated method because it involves examining today’s forecast scenario and remembering a day in the past when the weather looked very similar (an analog). The forecaster would predict that the weather in this forecast will behave the same as it did in the past.

For example, suppose today is very warm, but a cold front is approaching your area. You remember similar weather conditions happening last week, also a warm day with cold front approaching. You also remember how a heavy thunderstorm developed in the afternoon as the cold front pushed through the area. Therefore, using the analog method, a forecaster would predict that this cold front will also produce thunderstorms in the afternoon.

The analog method is difficult to use because it is nearly impossible to find a perfect analog. Various weather features rarely align themselves in the same locations they were in the previous time. Even small differences between the current time and the analog can lead to very different results. The argument in favor of analog is that as time passes and more weather data is archived, the chances of finding a “good match” for the current weather situation should improve, and so should analog forecasts.


Numerical Weather Prediction

Numerical Weather Prediction (NWP) relies on supercomputers to predict the weather. Massive supercomputers, complete with software forecasting models, help meteorologists make weather predictions based on multiple conditions in the atmosphere such as temperatures, wind speed, high and low pressure systems, rainfall, snowfall and other conditions.

Meteorologists review the data to determine the weather forecast for the day. The forecast is only as good as the algorithms used by the computer’s software to predict the weather and the data is overwhelmingly limitless. With advanced calculations and the ability to analyze numerous factors at once, NWP provides the best means of forecast the upcoming meteorological conditions when compared with the other methods.


Alternative Weather Predicting Methods

Did your mom ever say, “Red sky at night, sailors delight.  Red sky at morn, sailors take warn”? Mine did. Outside of the standard and more advanced methods used by professionals, there are numerous, less-conventional ways to predict the weather.

Here are a few signs to watch for when predicting a hard winter:

  1. Woodpeckers sharing a tree.
  2. Early arrival of the Snowy owl.
  3. Early departure of geese and ducks.
  4. Early migration of the Monarch Butterfly.
  5. Thick hair on the nape (back) of the cow’s neck.
  6. Raccoons with thick tails and bright bands.
  7. Mice eating ravenously into the home.
  8. Early arrival of crickets on the hearth.
  9. Spiders spinning larger than usual webs and entering the house in great numbers.
  10. Pigs gathering sticks.
  11. Insects marching a bee line rather than meandering.
  12. Early seclusion of bees within the hive.
  13. Muskrats burrowing holes high on the river bank.
  14. “See how high the hornet’s nest, ‘twill tell how high the snow will rest”.

The Persimmon Method

One particularly interesting method of winter-weather prediction comes via the persimmon seeds. According to folklore, if you crack op

en a persimmon seed from a ripe fruit and the shape inside (called a cotyledon) looks like a fork, winter will be mild; if you see a spoon, there will be a lot of snow, and if there is a knife, winter will be so cold it will “cut like a knife.”

Melissa Bunker of North Carolina, “The Persimmon Lady,” sends Farmer’s Almanac her winter predictions based on seeds she opens from the persimmon fruit grown on her tree in central North Carolina.  This year (her tenth year making predictions as a partner with Farmer’s Almanac), Melissa checked 100+ seeds and only two came out as forks– the rest were spoons, no knives at all.  In all of her years, she has never seen a prediction like this. She said, “This will be a winter for the record books in central North Carolina!” According to Melissa, “If you look back on the past years readings you can see the seeds follow 95% accuracy with the almanac.”


A Goose Wishbone as a Weather Predictor

Back before the turn of the last century and before the National Weather Service was in place, many looked to the breastbone of a goose for winter predictions.  Around Thanksgiving, a goose would be killed and cooked. The cook  would roast it, carve it, and serve it, always being careful not to cut the breastbone from the carcass.

After the goose had been eaten, they would carefully remove the breastbone and cut away all the meat and fat left clinging to it. Then they would take the bone and put it on a shelf to dry, keeping an eye out for the coloration that would follow. If the bone turned blue, black, or purple, a cold winter lay ahead.

  • White indicated a mild winter.
  • Purple tips were a sure sign of a cold spring.
  • A blue color branching out toward the edge of the bone, meant open weather until New Year’s Day.
  • If the bone was a dark color, or blue all over, the prediction was for a real bad winter.

An overall dark color meant that the goose had absorbed a lot of oil, which acted as a natural protection against the cold. The darker the blue coloring, the tougher the winter would be.


The Legend of the Wooly Bear Caterpillar

The Woolly Bear caterpillar has 13 distinct segments of either rusty brown or black. The wider the rusty brown sections (or the more brown segments there are), the milder the coming winter will be. The more black there is, the more severe the winter.

In the fall of 1948, Dr. C. H. Curran, curator of insects at the American Museum of Natural History in New York City, took his wife 40 miles north of the city to Bear Mountain State Park to look at woolly bear caterpillars. He collected as many caterpillars as he could in a day, averaged the reddish-brown segments, and then forecasted the coming winter weather through a reporter friend at The New York Herald Tribune.

Dr. Curran’s experiment continued for eight more years and attempted to prove scientifically the weather rule of the Wooly Bear Caterpillar. The resulting publicity made the woolly worm the most recognizable caterpillar in North America.

While most scientist do not take the wooly bear research seriously, there is a Wooly Worm Festival in Banner Elk, NC every October that celebrates this mini forecaster.  After a caterpillar race, the retired mayor inspects the winner and then predicts what the coming winter will be like.


Be Safe this Winter

Whatever way you slice it, dry it, or count it, Winter 2018 it tiptoeing in.  All predictions are pointing to winter coming sooner, with more intensity, and with increased snow.  Powerblanket encourages you to take the necessary steps to prepare for the cold ahead.

Winter Weather Predicting

Resin Curing Temperature

Resin curing + heat. This is something that isn’t discussed too much because, let’s be honest, it’s not a great selling point. The quicker and easier you can get your epoxy to cure the better, right? Resin curing temperature and curing time will vary depending on the mixture and manufacturer. While some systems are designed to ‘cure’ at room temperature, heat must be added for epoxies to reach optimal performance properties. Heat can be added via composite curing ovens, radiant heat, or epoxy curing blankets.

Types of Epoxy Resin Systems

There are probably several ways to categorize resin systems, but we’ll be focusing on two:

  1. One-part systems vs. two part systems
  2. Systems that cure at room temperature vs. those that require heat.

One-part systems vs. two part systems

While some systems are one part, most resin mixtures require two components. In one-part systems, heat is required to “kick-start” and maintain the curing process. More specifically, temperatures must be maintained around 250°F-350°F for a few hours (specific requirements vary).

Two part systems require the following elements: resin and a curing agent. Mixing the two initiates the chemical reactions necessary for curing.

Resin Curing Temperature: Room Temperature vs. Added Heat

As we’ve briefly touched on, heat requirements for epoxy curing vary from system to system. Quite often, all that’s required of two-part systems is mixing the resin and curing agent; the epoxy or composite is them able to finish curing at room temperature. However, some systems require additional heat. Again, the specific requirements of each system vary and can be obtained from the manufacturer.

Why Add Heat?

Knowing that room-temperature curing is an option, you might ask yourself “why would I want to go to the effort of adding heat during curing?” The key phrase here is “trade-off”. Adding heat usually means additional equipment and planning. However, epoxy mixtures that require heat boast the following properties:

  • Chemical resistance
  • Electrical insulation
  • Heat resistance

Hotter is Better!

It’s important to note that all epoxy mixtures (even those that ‘cure’ at room temperature) will technically not fully cure unless heat is added. Properly adding heat to systems designed to cure at room temperature will always boost the performance of the final product. However, curing at room temperature makes more sense when increased performance isn’t needed.

Let’s take a quick look at what this looks like in practice. Specifically, let’s look at how adding heat can increase the temperature resistance of a room-temperature cured system. Temperature resistance is measured by Glass Transition Temperature (Tg). Let’s say we have a room-temperature cured composite with a Tg of 100°C (212°F). When the composite is kept at 150°C (302°F), the Tg will increase by approximately 10-15°C (5-8°F). Keeping the product at the temperature for an additional 4 hours will increase the Tg by roughly an additional 5-8°C (1-4°F)


Many manufacturers use heat in a “post-cure” to achieve desired properties. This typically follows two simple steps:

    1. The epoxy is first left to cure at room temperature overnight. This allows the mixture to “gel” before heat is added. When heat is added to early, it can affect the viscosity. Drops in viscosity can cause the mixture to “run” and can lead to uneven texture in the final product.
    2. Heat is applied for a few hours. A good rule of thumb is to keep temperatures 50-100°C above the Tg of the epoxy. This “post-cure” boosts the epoxy’s performance without disrupting the texture or consistency.



Heat: What Are Your Options?

There are a few effective options for adding heat during the epoxy curing process. Knowing the pros and cons of each can help you determine which is best for your needs. 1

1. Curing Ovens

Composite curing ovens are a highly effective option that allow for precise and even temperature control. Additionally, ovens come in a variety of sizes; whatever needs to be cured, there’s an oven that can fit it. However, this option can be expensive to install and cannot be scaled up or down. Additionally, lack of mobility means projects must be transported to ovens for curing. 

2. Radiant Heaters

Radiant heaters are a more versatile and mobile option. They are notably less expensive than composite curing ovens and can be scaled up or down depending on the size of the project. Unfortunately, radiant heaters can cause uneven curing which leads to discoloration, bubbles, and brittle patches.

3. Heating Blankets

Heating blankets provide all the mobility and scalability of radiant heaters with significantly more precise and even temperature control. Unlike ovens, composite curing blankets allow the heat to be brought to the project (vs. transporting the project to a curing oven). This can save significant time and headache. For example, when repairs are done on wind turbine blades, rather than disassembling the turbine and transporting the blade to a curing oven, repairs can be done on the spot.


Powerblanket Epoxy Curing Blankets

Powerblanket Epoxy Curing Blankets utilize top-of-the-line heating technology to ensure even heat distribution throughout the curing process. Additionally, Powerblanket offers custom options; whatever your curing needs, we can help you develop a solution.

Pipeline Packaging: A Powerblanket® Partner

You’ll find heavy-hitting distributors like Pipeline Packaging are at the top of Powerblanket’s asset list. When it comes to getting our products to the people who really need them, companies like these are worth recognizing.

Pipeline Packaging: A Powerblanket Product Provider

A frontrunner in commercial and industrial packaging, Pipeline Packaging pushes everything from eye droppers to giant totes. Servicing an enormous range of industries, including HAZMAT, spill containment, health, beauty, food & beverage, paint, automotive, janitorial, pet and veterinarian, Pipeline has newly expanded their product line to Powerblanket heating and cooling solutions.

“We’re thrilled to expand our offering to include Powerblanket products,” says Tim Winings, VP of Marketing and Sales at Pipeline. “Our footprint inside the industrial and food markets makes this arrangement exciting for both companies.” Powerblanket affirms the sentiment.


Founded in 1988, Pipeline has spread to 8 states and 10 offices, and over $100M in sales. With their people-centric vision they always consider “Customer First.” Servicing countless businesses in the United States, Powerblanket is excited to work in tandem with Pipeline Packaging. With its reputable history, reach, service, and variety, Pipeline Packaging is an invaluable partner for Powerblanket heating solutions to both of our customer bases throughout the country.

Powerblanket Heating Solutions at Pipeline Packaging Include:

  • Bucket Heaters
  • Tote Heaters
  • Barrel/Drum Heaters
  • Bulk Material Warmers
  • Cooling Solutions