In the previous article we compared Commercial MR grade plywood with BWR plywood, and concluded that waterproof BWR is better than MR grade. This time around, let's differentiate between BWR grade and Marine grade plywood.
BWR grade means Boiling Water Resistant plywood.
It's a waterproof exterior grade plywood of good quality, that is suitable for most home furniture requirements. Most of the interior designers and carpenters, prefer to use BWR plywood for making kitchen cabinets and other kitchen furniture.
Marine grade plywood is of an even better quality than BWR grade, and used in conditions where the plywood is sure to get a prolonged exposure to extreme weather conditions such as even being submerged in water. It is the ideal choice for building ships, boats and other such marine applications.
What makes Marine ply so strong and water resistant, is the use of excellent quality wood veneers for making the plywood, and the use of unextended (meaning undiluted) phenolic resins. The resin Phenol formaldehyde is in fact a synthetic plastic resin, and that greatly increases the water proofing quality of Marine plywood. On the other hand in BWR grade ply, extenders are added to the resin, and it is diluted before using it to glue the plies together.
In the case of home furniture requirements using waterproof BWR grade exterior plywood is usually considered to be good enough, and the costlier Marine grade plywood is usually not used for such a purpose.
The important points of difference between BWR plywood and Marine plywood is summarized in the table below.
|BWR grade plywood||Marine grade plywood|
|BWR = Boiling Water Resistant||Marine Grade|
|Of lesser strength and quality||It is stronger and has better water resistance .|
|BWR grade is a waterproof plywood||Better waterproofing. Can be submerged in water for at least 72 hours without damage.|
|Diluted Phenol formaldehyde resin is used for glueing the plies together.||Undiluted Phenol formaldehyde resin is used for bonding the plies to each other|
|Exterior grade for outdoor use||Exterior grade for extreme weather conditions|
|Preferred for making kitchen furniture that is likely to get wet||Used in boat-building and other marine applications. Not generally used for making home furniture.|
|Indian Standards quality specification for BWR grade is specified in document IS: 303||Indian standards specification for Marine plywood is detailed in document IS: 710|