Best practices in your mixing room

Restoring a car to its pre-accident condition is a more complex procedure than it appears. Add to that making a profit in an ever-more competitive industry, and repairers face challenges daily. Like any problem, the best way to solve a large and complex dilemma is to break it down into its individual parts. By isolating and correcting those areas, gradually the problem will no longer look so overwhelming. One of the areas we must continually examine to control costs is in the refinish department.

It has been said that in painting, there are so many uncontrollable variables that painters should pay strict attention to those they can control. There are so many variables that can – no must – be controlled, but are often overlooked. Painters spend so much time mixing formulas, cleaning equipment, recycling solvent and focusing on the normal routine of working in the mixing room that areas they know should be checked or maintained are sometimes pushed aside to get the job finished.

Too often, however, the paint work suffers as a result. Some of the difficult-to-correct and costly mistakes, such as a corrupt bank, can happen even when slight errors are made, and the consequences may not be apparent until long after.

With the addition of new products, such as waterborne paint, there are advantages, but also challenges that must be faced and integrated into the routine. One of the areas that can present special challenges to productivity and profitability is the mixing room (Fig 1). .

Depending on your geographical location, paint mixing rooms are likely to have mandated regulations, and you should check for state and local requirements in your area. Whether your mixing room is a manufactured one attached to the booth or not, its ventilation needs to be maintained. The filters, both intake and exhaust, should be checked and changed regularly.

Solvent vapors are generally heavier than air, so they will lie at the bottom of the mixing room. The ventilation should be drawn off from the floor and brought in from the top or at the upper end of the wall.

The mixing room should be kept clean, and although this is much easier said than done in a busy paint room, it is still one of the best practices. The room should be kept clean from dirt, spills and clutter. Dirt in the room will almost certainly find its way into the mixed paint. To avoid that, the room should be cleaned on a regular basis.

The toner mixing rack should be maintained as well. The machine and all other potential spark-producing objects should be bonded with ground straps. Even static charges from plastic containers could be catastrophic. Empty containers should be disposed of as they accumulate, as mixing rooms can quickly become cluttered, leading to potential mishaps. Spills should be cleaned up, according to local requirements, immediately.

Two very good tips for paint room best practices are: 1) As materials are used up and new ones put in their place, the old labels should be placed on the clipboard in the mixing room, so that at a designated time a restock order can be placed. 2) Waterborne paint, which has a limited shelf life when opened, should be marked with the date it was opened (Fig 2). .

As toners or other supplies are used, a tracking system for restocking should be established. Though it may sound obvious, toners should be kept in a logical order on the mixing machine, and as soon as they are used, the spouts should be cleaned and their containers placed back on the mixing bank. If all the toners for a formula are taken off the mixing bank, or if a toner is not replaced as it is used, grabbing the incorrect one is more likely.

Paint materials are costly, and if an incorrect partly mixed formula must be discarded, it severely impacts profits. Toner lid fit should be checked regularly, as should the mixing bank for proper operation. Check that all the toners are mixing as they should. Those toners that aren't used as often as others may evaporate solvent from a poor-fitting lid, or a top that doesn't close completely because paint debris was not cleaned off.

Follow mixing formulas completely and carefully. Toner mixing guidelines have changed with the introduction of waterborne paint. Some no longer need to be regularly mixed, while others, both solvent-borne and waterborne, still have mixing recommendations.

Many paint manufacturers recommend that the toners be agitated for 15 minutes at the beginning of the day and at one other time during the day for 15 minutes. There are some coatings that should not be overmixed, so each painter should know and follow the recommendations of the manufacturer for its specific product.

Keep mixing scales clean, level and calibrated at all times (Fig. 3). Some scales have leveling feet that can be adjusted. If the scale does not have a level bubble, the scale should be adjusted with a small torpedo level, both with the pan off and on, to make sure that the pan supports are not bent and are holding it at level. .

Some scales will indicate a fault code such as "L" when the scale is out of level. Both the pan and paint table should be kept clean. Though a scale will zero out the weight of a spill, if the paint is not in the can, it is not in the mix.

Calibrate the scale occasionally according to the manufacturer's recommendations. If this is something that you do not have the tools or knowledge to complete, your jobber will likely be able to do it for you. If the scales pan has dried paint all over it, it could be either out of level or out of calibration. The accuracy of a scale, especially when mixing small amounts of paint, is critical to the color match.

In fact, some scales are so sensitive that the manufacturer recommends that they be turned on and let "warm up" for 30 minutes before use, especially when large temperature changes have occurred.

Corrupt bank

A corrupt bank occurs when a toner is poured off without being agitated, or before it is in correct suspension. Though sometimes a painter can tell by looking at the paint as it comes out, at other times it is not so obvious. If a toner is poured off in this state, that formula mix will not match. But more importantly, the colors mixed with that corrupt toner are likely not to match either.

This mishap can occur without being noticed, and the painter may look for other possibilities before discovering that the bank has one or more corrupt toners.

Even if the painter suspects a corrupt bank, finding the toner or toners that are bad is difficult. The painter must keep track of the formulas that are a mismatch and correlate the common toners to narrow it down and find the correct one or ones to replace them.

This is a difficult and tedious process, but it can be avoided by proper agitation. Some paint manufacturers recommend that a new toner be placed in a shaker for as long as 30 minutes before attaching an agitation lid and placing it on the mixing bank.

Shelf life

Though shelf life is not an issue with most solvent-borne paints, which can last for years if they are kept from drying out, waterborne toners will go bad if not used in a certain time. Unfortunately, most products have multiple shelf life limits that need to be considered.

There is one shelf life from the time of manufacture until the product should be used. There's another shelf life from the time a product is opened until it is used. There is also a shelf life, sometimes referred to as pot life, referring to the period from the time the paint is reduced until it is used. Even though a hardener was not added, the paint has a limited amount of time for which it remains "good." Painters should check with their jobber or manufacturer for their brand's recommendations.

Pouring of toners

Although there are now computerized pouring machines (Fig 4) for precisely mixing formulas, most of us still do it manually. Using some specific techniques will help with accuracy. Formulas, especially small ones, must be mixed precisely. Every number must hit correctly. Even if the computer will re-calculate the pour, there may not be enough room in the container, and if the correct amount of paint was calculated, the recalculation might overflow the container. .

Hold the toner so the pour hits the center of the container, (Fig 5). Don't rock the can back and forth to control the amount of paint that comes out. Hold it so that the paint will freely flow out when the gate (Fig 6) is opened with the thumb or finger. It's OK to start the pour at a fast rate and slow it down by partially closing the gate, as the amount reaches the correct weight. Some scales may need to catch up with a fast pour, so be careful as you near the desired amount. Pour precisely. If you believe that +1 or –1 is OK, you may get away with it sometimes, but the times you don't will be costly.

Calculating the amount of paint needed

One of the best practices for increased profitability in the mixing room is precisely calculating the amount of paint that will be needed to complete the job. Many computerized mixing systems have paint amount calculation protocols provided (Fig 7). .

Calculating the precise amount of paint needed can greatly reduce the amount of cost per job. If the amount of paint initially mixed is not enough and additional paint is needed, two challenges to productivity arise: 1) The amount of time needed to remix a formula is wasted time. 2) The amount of paint needed for the second mixing will likely be considerably less than the original, and therefore more difficult to pour because each ingredient is smaller, and thus it is harder to be precise. It is not always easy to calculate the amount needed. . Consider variables such as how quickly the color will cover, panel size and a specific brand's coverage ability. These are variables that painters need to be familiar with so that they can become increasingly accurate in their calculations.

Obviously, if more paint than needed is mixed, it will either need to be disposed of or stored, both of which can be costly.

As a rule of thumb, which should only be used as a starting calculation, with many solvent-borne paints, 4 ounces of ready-to-spray (RTS) paint will be used per panel, per coat. Therefore, if a panel will require three coats, 12 ounces of RTS basecoat should be mixed. If the reduction is 1 to 1, then 6 ounces of formula should be mixed. This calculation assumes that one panel equals an area of approximately 3 feet by 3 feet. Some panels, such as a fender, may be only one panel, while other panels, such as a hood, may need to be considered two panels. Remember, this is a starting point only, and the guideline will need to be adjusted for each paint system.

Labeling

If the paint is mixed just before it is used and the precise amount is calculated and used, there may not be a need for labeling. But if it is mixed on one day and used on another, even the next day, the container must be labeled; otherwise, mistakes are too likely to occur.

Silver is a common color, for example, and although two silver paints may each appear to be quite different on vehicles, they may be hard to distinguish as liquids. Labeling not only is required by law, but it is a wise practice to improve productivity and profits, as well as to avoid future frustrations.

It may seem that all of the procedures mentioned, if done as recommended, could keep a painter from being productive. Some of the steps, such as cleaning, maintenance and restocking, can be delegated to someone other than the painter; but other tasks must be done by the technician. The bottom line is that making a process, assigning the appropriate time intervals and carrying them out as designed will save valuable time. Mixing room routines make a paint department even more efficient and profitable by reducing the chance of color mismatches. When you consistently use a well thought-out process, variables can be controlled.