Tips to Keeping Panels Flat

I will likely keep mentioning this when we are making the one in cherry for the filming but it is important to sow the seeds now.

Progressing the prototype for a more compact, Shaker-style dresser slowed down a little with my Texas trip and then catching everything up for Christmas and the holidays coming up. With everyone gone from the studio I have had a little self-time working alone, which is now much rarer than it was in times past. This project has some simple elements I am complexing with added joinery features that will allow for expansion and contraction and at the same time hold everything together. Today I polished off the housing dadoes so I am ready for the divider frames that both fit into the housings but then dovetail to pull the sides in and keep them there. I have also designed the divider frames between the drawers to take mortise and tenons in an area where expansion and contraction will take place so that the M&Ts slide with any atmospheric  influence. Of course no one except those watching the video series will ever see this feature or understand the complexities. Most people don’t know that wood does indeed shift throughout its life after being converted and made into a project even though they might use the term shrink. We woodworkers better understand it because it so determines how it and we work.

 

There are some things I have done consistently over the years because of the influence of drying, expanding and contracting and such that’s really helped with the time span I might not normally experience but others likely will. One was to keep the clamps on after the glue up. Two, adjust the tightness of the clamps without squeezing the wood to death and bruising it; so just taking up the slack each morning. Three, blanket wrapping at the end of the day having stacked the three boards face to face first. Four, shrink wrapping the panels if indeed I removed them from the clamps for an extended period. Usually that’s when `i am working on the wood rather than just being ready to work on it. I have found that keeping clamps on or reclamping with opposing clamps as you do for glue-ups of panels, keeps the boards or panels flat by disallowing movement that would otherwise result in distortion. This is especially so with softwoods, but some hardwoods too. Clamping disallows this to happen in the first place. In this case five opposing clamps is enough. It works. Point five, keep the work away from any localised heat sources as much as possible. Even or especially passive sources such as sun through windows, which people commonly forget in homes. Radiators, heat stoves, especially when they’ve been off all summer. Especially is this so with new work, by the way, because mid sections of wood retain moisture longer.

 

My workshop seems fairly constant with regards to humidity. Over a four week period it seems that the boards shrank daily and then stopped. I good test besides loose clamps is to measure widths (not lengths because wood shrinks negligibly in its long axis) to see what the lose. You can also use weight too.


Tonight I blanket wrapped at close. Once the joints go together the joints too will constrain movement as will glue and fastenings. It is an especially good idea to use shellac on what will be endgrain areas such as tabletops as this ensures much more even shrinkage and it matters not when you do this so why not apply two or three coats sooner than later?

7 Comments

  1. Matt McGrane on 22 December 2016 at 9:17 pm

    What in the world does “blanket-wrapping” do to limit wood movement when the panels are stacked face to face?



    • Sigurt on 22 December 2016 at 10:12 pm

      It probably slows down any temperature and humidity changes to the wood, caused by the surroundings. It may even help absorb moisture released from the wood, rather than leaving the moistened air around the other panels.
      Just my guess.



      • Evan on 23 December 2016 at 9:02 pm

        Considering that looks like a wool blanket, that is probably accurate. Probably also helps slow tempature change and insure even change through the stack.



    • Paul Sellers on 23 December 2016 at 8:24 am

      Just slows down the exchanges in moisture levels overnight.



  2. Jeremy on 23 December 2016 at 3:17 am

    It does slow it down. I used cheap furniture moving blankets. I just completed a shaker drop leaf table for my mother’s Christmas present. The top and attaching the top was the most annoying part of it.



  3. Chris Hyde on 23 December 2016 at 2:48 pm

    Hi Paul,
    It was nice to meet you again at Harrogate. I tend to make up my own panels for furniture from something like 6 *1 boards and have not had any problems. I alternate the grain on adjacent boards and find they come out pretty flat even without the use of biscuits or dowels for levelling. What are your thoughts on using ready laminated pine and hardwood panels, the lamels are usually 40mm. It seems most commercial furniture is made this way.
    Regards Chris



    • Paul Sellers on 23 December 2016 at 5:58 pm

      I have never dowelled panels together because I never saw the need and the same is true of biscuits and biscuit jointers too. I did own a biscuit jointer for a brief while but in the end it just gathered dust alongside other such equipment. We all develop techniques and adopt methods for different reasons and then try methods to see what works for us. In my case I use a technique I have developed that’s worked perfectly for aligning all but the largest panels for me for decades; it’s fast and effective. Old dogs–new tricks? Maybe. I just felt like it was another unnecessary piece of equipment for me. Oh, and in all my years I have never had a glue line fail, so I suppose that proves glue. I have bought a couple of panels of ready glued panels once from a flea market for 20p and used them. They were fine once I painted them–stayed flat and everything. I think the sophisticated equipment and adhesives used in the commercial sectors are efficient and strong. I see no problem with using them as long as they are grain and colour matched to suit your criteria.
      The question of alternating boards to arrange growth rings so that the counterpoise one another comes up frequently as many commercial operations use this to help boards resist creating a mono-convexing/concaving to surfaces used to make say wider surfaces such as tabletops and panels, cutting boards and so on. Here is the reason: Most commercial producers reduce the widths of wider sections of wood to under 3″ and flip them to alternate because it is more stable and more controllable. With very narrow sections this leads to less less decision making in the manufacturing process and of course the narrower the sections used the more uniform the surface patterns and colour. We on the other hand are picking our wood for what we want to create using colour and grain configuration to its optimal advantage and that’s what makes our work different to commerce. Unfortunately flipping is standard because people are fearful that omni-directional cupping will occur and ruin our endeavour. In reality this is more rare than the norm in my experience, even in extreme exchanges. Often flipping boards as has become standard even for individual makers like myself leads to a washboard surface because we tend to use wide surfaces rather than narrow ones.
      I took a pick of three panels I actually glued up around the 5th November and the panels have stayed really quite flat even though some have grain oriented all the same way and one has alternate flipping. I posted them on my blog here:
      Now of course the thicker the sections you are creating for panels the more problematic panels become and this is where alternating comes into its own. The thicker joined edges push the inner and outer surfaces further apart and of course that means that the surface fibres absorb moisture differently. That being so it is indeed better to use narrow sections as the wider the boards used the greater the influence moisture has and the greater the distortion that takes place. I have added some more info on a blog where I used your questioning here for a Q&A as I thought it would be quite interesting for others too.