Plywood refers to a board of wood that is produced by arranging thin sheets of wood by applying formaldehyde, melamine or phenolic glue. The glue is liberally applied on the thin sheets or ply of wood as they are commonly called and pressed under high pressure. This ensures that the layers do not split even when hammered with a nail. There are a number of factors that would determine the quality of the plywood and the plywood grades.
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The factors that determine the quality of the plywood
The factors that determine the quality of the plywood which is important for assigning plywood grades as well include
Overlappings- This is assessed by viewing the side profile of the plywood. The lesser the overlapping of sheets in the plywood, the better is the quality of the plywood.
Core gaps- This is again estimated by viewing the side profile of the sheet. It is indeed common for the plywood boards to have gaps between the different layers of ply that are bonded together. If it is greater than 2mm-3mm, it is indicative of poor quality and thereby fall under the lower plywood grade listing.
Nail holding capacity- This feature has got to do with the functionality of the plywood board. if the plywood chips or splits, it is indicative of poor quality.
Weight- The heavier, the board is, the better is its quality. Eucalyptus boards are considered to be heavy and of a higher quality.
Glue- The type of glue used for bonding the plies have a considerable role in determining whether the plywood is meant for exterior use, interior use or for use both in interiors and exteriors.
Certifications- In India, the plywoods are certified by the Indian Institute of standards. According to them, the various standards stand for different plywood grades. Which includes
- IS: 303- which is for commercial ply
- IS: 710- which is for Marine Ply
- IS: 1659- which is for blackboard
- IS: 2002- which is for flush door
- IS: 4900- which is for Shuttering plywood
Testing- This goes hand in hand with the certification and the plywood is tested on various properties it claims to feature such as boiling waterproof, fire retardant properties etc and plywood grades are assigned accordingly.
The plywood grades you come across are indicative of the presence or absence of the factors that are markers of the quality of the plywood in the board of plywood in question. It goes without saying, higher the grade, better is the quality of the plywood in question.
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The grades of plywood
The plywood grades you can access in the Indian market include
MR Grade Plywood– The MR here refers to moisture resistant plywood. This is one of the most common types of plywood that carries the Indian standards specification number IS:303. You should not confuse the term moisture resistant with waterproof. MR plywood is by no means waterproof in nature it can merely resist moisture and humidity. It is also known as commercial ply and features a formaldehyde glue that makes it suitable for use only in the interiors. it can be used to make furniture, but, it is mostly suitable only for furniture that would be kept away from water.
BWR Grade plywood– The term BWR refers to boiling water poof plywood. The glue used to bond the plies is phenolic in nature and is used in making plywood that stays together even if a block of plywood of this grade is cooked in a pressure cooker for about 5 whistles. It is suitable for both interior and exterior use and most suitable for making kitchen cabinets, furniture, paneling etc.
BWP – This refers to boiling waterproof boards that are almost similar in construction and glue used to the BWR plywood grades. But, one distinguishing factor is that BWR refers to plywood grades while BWP stands for blockboard grade. Hence, it is important that you do not get confused with the two grades.
Marine grade plywood– The marine grade plywood differs from the MR plywood in that it is highly waterproof and is quite strong enough to be used in marine applications as well. it includes even making boats. The marine plywood grade acquires these properties owing to the unextended or undiluted phenolic resins that are used for bonding of the plies under pressure. The high-quality wood veneers that have good weight are used in the manufacturing of the plies which make it an ideal choice for making home furniture that would be placed in areas where it would be in constant contact with water, for decks that are closer to the swimming pool, for making boats and ships owing to the properties that prevent it from danger even when it is submerged in water for more than 72 hours. It is suitable for use both in the interiors and exteriors and is the most expensive and high-quality plywood that you can ever have.
However, you have FR grade which is indicative of the fire retardant properties, Structural plywoods meant for industrial use, flexible plywood that can be rolled into sheets. Depending on the consistency with which the different brands produce different grades of plywood they may be termed as the best in producing a particular grade of plywood. The MR, BWR, and Marine are three plywood grades that are commonly used.
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