“This may seem like a silly question, but what’s the difference between liquid detergents and powdered detergents? How do their cleaning abilities and storage characteristics compare? Is one type more environmentally friendly than the other?”
CHEMICALS SUPPLY: Kevin McLaren directs the CLG (Commercial Laundry Group) Laboratories for the Dober Group, a manufacturer of specialty chemicals. He joined Dober in 1994 after serving 10 years as an applications chemist in the industrial and institutional housekeeping markets.
Powdered and liquid detergents are both used successfully in the commercial laundry, and each offers formulation limitations and flexibilities to the detergent industry.
There has been a fundamental shift in the wash-floor chemistries employed by the textile rental launderer over the past 10 years, with liquid products having gradually become the preferred product form. Many factors have driven this market shift in product preference, with differences in performance, storage and environmental profile being only a few selection criteria.
Both powdered and liquid detergent formulations are typically applied in a multiproduct system. The rationale for multiple products stems from, in part, the ability to craft desired wash liquor within the washer.
For liquid formulations, each product is somewhat limited by the solubility and compatibility of the formulation constituent in the carrier, typically water. Thus, liquid detergents are often based on high levels of surfactants and other surfactant-compatible materials, and liquid alkalis are typically based on liquid hydroxides and other materials that are alkali-stable.
Conversely, powdered detergents are formulated to contain alkali, water conditioners and surfactants; however, the amount of surfactant in a powdered detergent is limited, to a degree, by the need to have the powder flowing freely rather than being a solid.
The storage of powder and liquid detergents is also predicated on the needs of each physical form. It’s undesirable for powders to have a solid, or cake. Powder detergents can be hygroscopic (water-absorbing) and can be pressed or compacted, both which will adversely affect one’s ability to dispense a powdered product out of a drum or bag. Thus, storage of powdered products can be limited by how long the inventory will be stored prior to its use and by the quantity of weight that can be stacked.
Alternatively, liquid formulations can be stored in a variety of container sizes, ranging from 5-gallon cans to large, bulk storage tanks. A feature that is specific to storage of liquid products is secondary containment for bulk storage to prevent an accidental release into the general public. A second storage consideration for liquid products may be volume restrictions for products with a DOT (U.S. Department of Transportation) hazard rating, with the local fire marshal authorizing the quantity of allowable product.
The environmental profile of any detergent, be it powdered or liquid, is based on the individual formulation constituents and their synergies. Both powdered and liquid formulations are being developed to meet the evolving definitions of “green.”
Perhaps the greatest difference between powdered and liquid detergent formulations is the ability to dose liquid products to the wash floor via automated delivery systems. The ability to automatically and accurately inject liquid products has produced cost-saving alternatives to manually adding scoops of powdered product to each washer.
The automation of the liquid injection system has replaced the need for a wash-floor operator to tend to each washer at each wash step, resulting in labor savings. Additionally, the accuracy of liquid injection systems has improved control of the quantity of material being dosed to the washer at every wash cycle. This greater accuracy has eliminated overdosing and underdosing of powdered products, a scenario that is commonplace when adding powders via use of scoops, cups and buckets.
COMMERCIAL LAUNDERING: Richard Warren is the general manager of Linen King of Central Arkansas, a commercial laundry that provides COG, rental and linen distribution services for healthcare clients. His experience also includes OPL and industrial laundering, linen supply, and leather/fur cleaning.
I believe the decision between using powdered detergents or liquid detergents is more of an institutional or personal preference than anything else. Powders are stored longer and must be kept dry. However, in most cases, laundries will seldom have the chemicals longer than a month, so storage isn’t really an issue.
Many washers manufactured in recent years are equipped only for liquids, a factor to keep in mind if you’re in the market for used washing equipment. But most are adaptable to either style. The tunnels all use liquid supplies, as they require all chemicals to be injected at the same time, and, so far, it’s impossible to use powders in that application.
There are some powders that are dissolved into water and then handled as the liquid they become. Some are mixed in a specifically designed machine, while others are mixed at the point of use.
That type of product has some advantages from both worlds. Generally, when you think of powders, there’s an image of a washman measuring a powder and pouring it into a washer. There are specific scoops of different sizes and colors that measure the product. I remember the 3-pound coffee can for the large washers, 1-pounder for the small ones and, of course, we soured with the tuna can. If we saw something really soiled, we poured in another scoop. I wonder how we ever made any money.
The environmental impact is interesting. The packaging for dry chemicals will break down relatively quickly. However, the plastic drums or totes that liquids come in will be around for a long time. Also, if the containers — liquid or powder — aren’t completely empty, there will be some contamination of the landfill or wherever the packaging ends up.
I’ve used both styles and enjoyed success with both. The chemical reps tell me they have more latitude or options with powders. Most reps don’t care which style is used, and the good reps will perform well regardless of powder or liquid.
I prefer liquids, since there is less handling. They can be positioned in a remote area and pumped to the injection point at the appropriate time in the approved amount. This is about as foolproof as you can get.
LINEN SUPPLY: Bill Kartsonis is the president of Superior Linen Supply Co., Kansas City, Mo. He's the immediate past president of the Kansas City chapter of the International Executive Housekeepers Association (IEHA) and is a Master Hotel Supplier certified by the American Hotel & Lodging Association (AH&LA).
In our laundry, we’ve been injecting chemicals in liquid form into washing machines for 40 years. It seems so natural now.
Control is the main reason that liquids are preferred. If a washer’s formula controller demands a certain chemical at a certain time in the wash process, it gets it.
In the old days, we had to rely on a highly skilled washman to choose the correct amount of each powder, scoop it up and dump it into the washer on schedule — usually at the ringing of a bell. If the washman was unskilled, you received poor results. It also was easy for the washman to try to “improve” the formula. After all, if a little chemical is good, isn’t more chemical better? You can understand why controlling the chemistry with programmed electronic controllers is better.
Along the way, soap salesmen would tell us that dry, powdered chemicals were better. Because I always felt that the guy just wanted to sell the old stuff he had in the back of his truck, I ignored the pitch. Later, I learned there is an element of truth to what he was saying.
In science class, we learned that matter has three states: solid, liquid and gas. Some items are stable only in one state. Often, the state depends on the temperature, pressure and other variables. Some chemicals are stable as a solid (powder) and not as a liquid, meaning their cleaning abilities are only available if they are scooped in by hand.
A few years ago, a well-known laundry chemicals supplier introduced a “pumpable powder” which has, in fact, improved our formulas. The powder is suspended in a liquid and then pumped using the same pumps that move liquid chemicals from barrels into the washers.