Multi-Species Marine Traps
Used Aquaculture & Processing Machinery
Fukui's Monthly News Letter
How to choose quality netting
In the last issue (FFN March/April 1996) I discussed the cost of gear, and how to determine the best business purchase by considering labour, handling efficiencies, and quality. This column will focus on the quality question: How to define and recognize quality in netting and how to make sure that you are getting what you are paying for.
The materials commonly used in netting material are Polyethylene, Polypropylene, Nylon and Polyester. There are a number of exotic and semi-exotic materials that are less common. There are also the ridged and semi-ridged materials that are used for different applications dependent on the end use and species farmed.
Almost all these products are derived from a petroleum base and in their raw form are called resin.
In most cases, the material is supplied by the chemical company to the net manufacture in the raw or pellet form. The net manufacture extrudes the material into fibers that are eventually spun into twine and then woven into net. There are also the extruded and die molded netting products that are commonly used in mussel socking and oyster trays.
Manufacturers do not all follow the same standards and that results in differences in quality of the final product.
Resins come in both "A" quality and "B" quality with "B" some times being half the price of "A". Before they are extruded, both "A" and "B" resins may be mixed with color enhancers and/or ultraviolet (UV) inhibitors, and each process adds to the final cost.
UV inhibitors, on the other hand, can be the single biggest reason for increased cost of netting products. The inhibitor typically costs about 10 times as much as "A" resin. Even though the mixture ratio is relatively small, it can make a big difference in the final price.
A good quality net product is "A" resin with the maximum allowable amount of UV inhibitor and the color of choice. The low quality alternative is "B" resin with no UV inhibitor, which is probably less than half the cost. So which grade of quality should you choose? You will probably remember back when polyethylene and polypropylene yellow colour rope first arrived to the market place. As it became popular, the price dropped. The pressure to push the price down caused the quality to be compromised, however. If you remember, the last yellow rope you purchased may have lasted only a few years before it started to fuzz, rot and break down due to exposure to sunlight (UV). As a result even the "good" yellow rope is now "poor" quality and you would probably not use it commercially.
Do not let yourself get caught up in the group of individuals claiming that since the nets are in the water, UV degradation is not a problem. If there is little or no UV inhibitor it usually means "B" quality resins. That results in a short life span.
I saw some pearl nets last year that were left in an open box near a window that sunlight shone through. They were in the same position for almost six months and the edges had all faded a lighter colour as a result of almost no UV inhibitor in the resin. These nets had not even been in the water yet and were already showing signs of deterioration. That farmer will learn an expensive lesson as the nets would be lucky to last 2 or 3 years at the most, instead of the 5 to 7 years that careful treatment should provide.
Once you know the quality you want to buy, the obvious question is: How can you tell if the gear you are buying is "A" quality, maximum UV protection, vs. "B" quality, very little or no UV protection? Unfortunately there is no easy answer since there are no international labeling requirements or recommended UV ranges.
Low quality polyethylene and polypropylene will usually be dull in appearance and will not have a sheen to it, as does the higher quality material. That is not always true, however.
The country of manufacture can be another indication of quality. There are many cases of Third World manufacturers supplying on price alone; quality is sometimes not an issue.
You need to be aware, however, that there are also some manufacturers from countries such as Japan, who have focused on quality for decades, that have brought in their own quality control managers and are supplying a very high quality, lower cost product from their own plants or joint ventures in Third World countries.
Price, at this point, is still the only real way for the farmer to judge quality. Beware of the very low cost as well as the very high cost product. Question the supplier about how long the product should last; ask who manufactured it, and, finally, request evidence from the field that supports the supplier's claim.
It won't take you long to find out which suppliers are there to answer you questions and support you long-term with quality products.