Electrostatics and Finishing
Q. Could you send me info on how electrostatic works with spraying for woodworking?
A. Rick Hill responds The use of electrostatics on wood has been around for awhile. As a general overview, most industrial finishers use electrostatics when they are coating parts that are hard to spray evenly. Common applications would be cribs or bed ends where an electrostatic can coat the dowels evenly without the usual overspray seen on sprayed applications.
The wood is the negative pole so the coating carries the positive charge.
The drawbacks are that you are dealing with a very flammable combination of products...solvent based coatings, wood and electricity. Very specialized equipment and specific coatings are needed before this is a feasible method to use. It is also a system that requires excellent operator training and consistency to stay safe.
As to cost, once the equipment is set up, they are similar to other coatings, but the equipment cost is the biggest investment hurdle.
Rick Hill is an independent representative and consultant for industrial wood finishes. He has been involved in the woodworking industry for 12 years, and has been known to actually hold, shoot, and clean a spray gun.
Comment. Michael Michalski responds:
First, the wood is not a negative pole. Electrostatics create the negative pole or charge which is picked up by the paint particles. The substrate, in this case wood, must be positively grounded. Some woods can contain enough moisture content to allow them to be positively grounded, but most do not. There are several methods for achieving a positive ground on the wood. One method is to fog the wood with a saline solution to create a conductive surface on the wood. Some manufacturers will use a conductive sensatizer in their stain which again forms a conductive surface on the wood. The wood can then be positively grounded. The negatively charged particles are then attracted to the positively grounded part.
Second, both manual and automatic guns are intrinsically safe. They incorporate current limiting technology that can sense the proximity of a grounded object and instantly reduce voltage to prevent ignition of the substrate. What few fires that have occurred in the last forty years of use are insignificant when compared to the numbers of guns in use. Most of these can be attributed to improper use of the equipment or insufficient maintenance of the equipment and the grounding process.
Third, electrostatic paint formulations do not usually contain solvents with low flash points thus further increasing the safety of these systems. Fourth, water base paints are also commonly used in many electrostatic wood finishing systems. The issue of operator training and maintenance is true but the payback on material savings and labor is usually substantial and more than pays for both the initial costs and maintenance costs. If I can be of further assistance to you, please feel free to contact me.
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