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Tips & Tricks

Veneer finishing is probably one of the most delicate subjects of our craft and has been the cause of many tears. Finishing problems find most of the time their origin in combination of events which none of the actors were controlling fully.

 

Over the years, Finaspan has made up a good deal of knowledge. We have listed on this page the most commons situations and what actions to undertake to avoid problems. 

 

If you wish to finish boards yourself, don’t loose of sight a couple of tips. First of all, never loose sight of the fact that veneer is not solid wood; it is barely a few tenths of mm thick and has had to be jointed one way or another and bonded to its substrates. This means that on the other side of this thin layer of wood you will find either glue or zig-zag, or both and you will have to avoid the finishing products crossing this layer and coming into contact with the adhesives.

 

In addition, never try to save on sanding before the application of stains and varnishes. Our boards are sanded with grit 120, but for a good finish it is recommended to prepare them successively with grit 150 and 180. From a general point of view, our panels are properly sanded, but we can never rule out that, due to circumstances (difference in thickness in the carrier, tension in rigid and thick panels, porous veneer), glue traces may remain somewhere. Before you start staining, make sure that the surface is completely free of glue traces and if necessary touch up until everything is gone.

 

There are also countless finishing products, but also countless types, which have evolved in countless different environments. Any combination can have unexpected results, for which we cannot necessarily be held responsible.

 

So, one last piece of advice: if you want to avoid unpleasant surprises, always take a test!

About veneer

Flake or Medullary Rays

Is  flake  a  defect ?  This  question  is  a  matter  of  endless  discussion  but  before  answering,  we  have  to  explain  to  you  what  flake  is  exactly.  And  first  of  all,  what  it  is  not : a  veneer  defect ;  and  secondly  what  it  really  is :  a  perfectly  natural occurrence .

                        In  each  tree  we  find  very  thin  cells  whose  function  is  to  redistribute  the  nutritive  materials  from  the  cambium  ( sapwood )  to  the  heart. In  hardwood  species,  these  are  called  « medullary rays ».                   

                        By  most  species  these  rays  are  so  thin  as  to  be  invisible. In  some  cases  however,  they  show  up  clearly  and  are  called  « flake ».  For  example  Oak,  but  also  Lacewood,  Louro  Faïa  and,  to  a  lesser  degree,  Beech  and  even  Mapleshow  us  a  well  pronounced  flake.

                        These  rays  cross  the  growth  rings  with  a  90 °  angle  and  because  of  the  cut  angle it  is  in quarter cut veneer that  flake  is  shown  to  us  with  all  its  brightness.

                        Composed  of  hard  and  dense  cells,  flake  is  as  fragile  as  crystal  and  doesn’t  react  to  stains  and  lacquers  as  does the  rest  of  the  veneer ;  for  this  it  is  unfairly  criticised  by  those  who  wish  to  stain  or  lime  Oak  or,  more  simply,  to  speed  up  a  lacquer  finish.

                        For  centuries  however,  Oak  flake  was  appreciated  and  even  sought  as  it  was  the  distinctive  sign  of  a  valuable  wood ;  those  who  couldn’t  afford  to  pay  for  it  would  even  copy  it  by  painting  on  cheaper  wood …

                        Even  if  times  are  changing  and,  with  them,  our  perception  of  things,  Oak  does  not  change !  It  should  therefore  never  be  forgotten  that  flake  forms  an  integral  part  of  quarter  cut  oak  veneer ;  only  a  very  small  proportion  ( +- 2 % )  of  veneers  produced  from  a  log  can  claim  for  appellation  « straight  grain  without  flake »  and  even  then,  the  start  of  a  half  crown  on  an  edge  will  not  always  be  avoided,  except  on  true  Rift  production  on  a  Stay Log  machine,  but  in  such  case,  the  grain  will  never  be  perfectly straight :  it  will  always  deviate  slightly  to  the  end.

                        As  these  veneers  are  very  rare,  they  are  automatically  most  of  the  time  very  expensive …

                        Those  who  are  looking  for  straight  grain,  narrow  and  without  flake  will  find  an  advantageous  alternative  in  Quarter  Cut  Larch  or  Oregon  Pine.

                        Strangely,  the  market  doesn’t  build  up  the  same  presumption  against  flake  in  Lacewood  or  Louro  Faïa :  the  larger  the  flake,  the  more  these  two  species  will  be  appreciated  but,  once  more,  this  is  not  the  most  common  occurence.

Half Crowns and False Quarters

We  have  seen  above  how  veneer  was  sliced  in  crowns  and  quarters ;  in  practice  however,  things  are  not  so  obvious :  when  you  slice  half  a  log  indeed,  there  is  a  moment  where  the  knife  is  reaching  the  core  of  the  log ;  as  this  part  is  unusable,  the  flitches  will  have  to  be  opened  in  a  first  step ,  then,  in  a  second  one,  the  log  itself.

 The  result ?  a  substantial  proportion  of  veneer  in  half-crown  and  false-quarter  ( +-30% ).  It  is  therefore  unreasonable  to  expect  large  quantities  of  boards  in  full  crowns  only  ( neither  in  full  quarters too )  in  species  where  the  market  is  not  very  large ;  on  the  other  hand,  when  you  fade  from  the  crowns  to  the  quarters,  you  will  also  come  across  half-crowns  which  will  have  to  be  classified  somewhere ; except  by  particular  agreement,  half-crowns  are  classified  among  Crowns.

Streaming

Steaming  has  the  objective  to  make  the  wood  softer  in  order  to  make  the  slicing  operation  easier.  But  it  also  modifies  its  colour ;  the  art  consists  in  trying  to  achieve  the  most  uniform  colour,  regardless  of  the  production  or  the  origin  of  the  batch.  Steaming  however  is  not  an  exact  science  and  many  factors  come  into  play.  Therefore  you  must  expect  some  variation  from  one  log  to  another.  On  the  other  hand  it  is  important  to  note  that,  if  some  species  are  mostly  steamed  for  slicing,  they  are  not  necessarily  steamed  for  sawing ;  colour  variations  between  solid  wood  and  veneer  should  therefore  not  always  be  completely  excluded.

American Oak versus European Oak

Some years ago, under  market  pressure  ( mainly  prices )  European  Oak  had  been  more  and  more  replaced  by  North  American  Oak,  finishing  with  a  sometimes  damaged  reputation.  Of  course,  American  Oak  was  generally  lighter  in  colour  when  it  was  freshly  sliced,  but,  if  European  Oak  was  sometimes  darker  indeed,  it was  above  all  a  question  of  drying ;  with  appropriate  drying,  it  is  perfectly  possible  to  produce  European  Oak  veneer  of  a  fairly  light  colour.  Meanwhile, all European producers have adapted their production process to the expectations of the market and the Oak veneer is now dried at low temperature what enables the veneer to keep its nice light colour. Actually  it  is  more  a  matter  of  shades :  American  Oak  is  moving  in  the  grey  shades  when  European  Oak  is  moving  in  the  brown  shades.  With  time,  European  Oak  will  actually  take  a  much  warmer  sheen  which  explains  why  it  has  the  favour  of  parquet  flooring  producers.  In  conclusion,  don’t  throw  the  anathema  on  one  Oak  or  the  other  according  its  origin ;  simply  learn  to  appreciate  good  things  and  make  your  choice  in  function  of  objective  considerations.

Reception of boards

Control before machining

Just before cutting the boards you discover some defect or a character that you don’t like. Please hold on ! Under all trade agreements, a cut board is an accepted board. If it doesn’t suit you for whatever reason, pass the message to us and let’s agree together over the next step. A board that you send back will have a certain value for the producer. Once cut and refused afterwards, it has no value for anybody else which will just increase the bill.

Storage of boards

Storage

Whether you are a distributor or a user, sooner or later you will be required to store decorative veneered panels :  protect them well !  These panels do not always stand up well to a long period of storage, as the veneers are sensitive to light, moisture and dust.  A simple cardboard covering will therefore only protect your boards during transport or during 2/3 weeks in storage.  If some of your panels are likely to remain in storage for a period of months, it is important that you protect them with a covering panel, preferably rigid, or at the very least applied over the entire surface and held in place with a certain amount of pressure to prevent damp air or dust from spoiling the veneer.

Application of a clear or coloured varnish finish

After applying the final coat, the differences in colour between the strips of veneer are further emphasised causing an unattractive dark and light effect.

During the slicing process, the pores of the wood are cut on an oblique angle and reflect light differently according to the incidence angle.  A lighter coloured strip will appear darker if looked from the other side of the panel and vice versa.  A clear lacquer will only make this phenomenon more obvious; this is particularly visible on quarter cut veneers.  If this light and dark effect disturbs you, ask for a slip matched or a random matched veneer. The differences of colour will be minimal but above all the repetitive effect will be gone.

Application of a stain followed by a lacquer

Small bubbles by finishing

The bubbles indicate the presence of moisture during the application of the final coat, possibly with a spray gun.  The water repels the lacquer and then evaporates, leaving small bubbles or craters.  Resand  and start again, taking care to work in a dry environment.The bubbles indicate the presence of moisture during the application of the final coat, possibly with a spray gun.  The water repels the lacquer and then evaporates, leaving small bubbles or craters.  Resand  and start again, taking care to work in a dry environment.

Application of a linseed oil

Natural wood colours

White marks when staining

The stain has come into contact with the layer of glue bonding the veneer on the substrates. It is possible that this is due to bleed through of glue, but it is also possible that the veneer has been over sanded or that the stain has penetrated too deeply. If you are faced with a problem like this and are caught by time, there is however to get rid of the problem quite easily.

 

                        Most stain producers manufacture what could be called an "isolator". This is a product that is applied as an under coat and which fills the bottom of the pores of the veneer in such a way as to create a uniform barrier at a depth of 0.2 / 0.3 mm over the entire surface. Next, the stain can be applied as a second coat: obviously, it will penetrate less deeply and the contrasts will no doubt be less marked, but the stain will be more uniform and free of blotches.

Regarding the stability of natural wood colours

The colours of most species of wood are each more beautiful than the next.  They are not permanent, however, and will change under the effect of light and moisture. Paradoxically, light species will become darker and dark species will become lighter. In fact, over time, all species turn grey ! Hence the importance to avoid direct exposure to sun light and to apply a good finish protecting the wood as well as possible from both UV and humidity. 

 

Certain species, however, take a few days for the fullness of their splendour to show. This is true of African Mahogany ( Khaya ) and European Larch, which both take on their brighter sheen after a matter of months or years.

Careful with the finish

A final comment

The colours of most species of wood are each more beautiful than the next.  They are not permanent, however, and will change under the effect of light and moisture. Paradoxically, light species will become darker and dark species will become lighter. In fact, over time, all species turn grey ! Hence the importance to avoid direct exposure to sun light and to apply a good finish protecting the wood as well as possible from both UV and humidity. 

 

Certain species, however, take a few days for the fullness of their splendour to show. This is true of African Mahogany ( Khaya ) and European Larch, which both take on their brighter sheen after a matter of months or years.