# Introduction

Although there are infinite possibilities for materials to work with. At Opendesk we have chosen to concentrate on sheet plywood to start with. There are numerous reasons for this such as strength, reliability, ease of use, etc, but we’ll get into that later. You’ll see below that even with the narrow focus on sheet plywood there are still multiple options and considerations. We’ve summarised our learnings below so you can wrap your head around what’s available. Wood is a natural product and therefore can come with defects, we’ve summarised these for you in the next block

# Defects

Pin Knots: Small knots generally filled and under the size of a small coin.

Mineral Streaks: Natural marks where the tree has absorbed minerals from the soil during its growth. can come in varying sizes and colours.

Patches or Plugs: Used to repair otherwise good quality sheets, patches can be oval or irregular as above and are used to repair defects such as open knots.

# Birch Faced Plywood..

Birch Faced Plywood is graded according to the two outside veneers. The grades indicate the quality of the veneer according to the number and type of defects allowed on each face. The grades are denoted by grade/grade describing the grade of the two outside veneers.

B/BB or S/BB (mostly synonymous) The top grade typically available. The B face should be free of any defects excluding one or two minor pin knots with a uniform colour. The BB face allows for a few small patches and some light mineral streaks. This is commonly available in 2440mmx1220mm sizing, but can be harder to get at larger sizes and typically will be lower quality.

BB/BB The general standard for industry. Both faces allow for a few discrete patches, some mineral streaks and filled knots. Depending on the batch BB/BB can vary significantly with some being closer to B faces and others being closer to CP faces. This is widely available at all sizes.

BB/CP Reasonably common, the CP face allows for unlimited patches and knots, but no open blemishes. We would typically not recommend this grade unless the batch is very close to BB grade. Widely available in all sizes.

# Pine Faced Plywood

Pine Face Plywood is typically more difficult than Birch to get a fully clean face, the grading reflects this as below.

A/B The standard premium option the A face allows for ~ 6 patches, no more than a few synthetic repairs, and small filler repairs. The B face is similar but allows for more repairs.

B/B Allows for ~6 patches, ~8 synthetic repairs and small filler repairs to knots etc.

B/CP The B face allows for a number of patches and repairs. The CP face allows for all types of repairs, however doesn’t permit open defects. We wouldn’t recommend using this for Opendesk projects.