Hi folks, I want to talk a little bit about Ash wood grain and issues with so called "waviness" in some areas. I have noticed this issue is a result of the deep grain lines that run through the body. There are areas that are smooth and flat that drop off sharply into the deep grain lines. Then slowly rise from the low area in the grain back to the flat higher smooth area. This rise and fall will cause the finish to look similar waves. The "waves" are most noticeable where there are curves in the body like the arm contour, belly contour and the back edges of the body. Some Ash bodies are worse than others. I have seen some ash that had very tight shallow grain and others that had deep wide grain. No two bodies are exactly the same.
Now I would like to talk about how to correct this issue. I need to touch base on some of the products used on the guitar bodies like nitrocellulose, grain filler and a catalyzed base/filler.
Nitrocellulose is an evaporative coating sprayed to the guitar. It will always continue to shrink showing anything going on underneath the finish (substrate) even if it was sanded level at first.
Grain Filler- most people think "grain filler" will level the deep grain lines in Ash, this is not true. Grain filler will only fill the pores enough to apply finish. The difference in height between the grain lines and the body will still be noticeable.
Catalyzed Base/Filler is the only true way to make an Ash body not show any deep grain lines and to minimize the "wave" effect. The catalyzed base does not shrink and does not react to solvents after it has cured. It usually takes 3-4 coats of around 5 mil per coat. Once the base is sanded flat it will stay flat providing a level substrate for the nitro.
So, if you like the grain line look of the early 50's Ash Fender bodies, you will only need grain filler. If you want an Ash body to be "dead flat" you will need the catalyzed base applied before the nitro.
I hope this helps clear up some of the misconception about the cause of so called "waviness" on some of the Ash bodies. I will post some pics below as a visual representation of what I'm explaining. Thanks
This is a cross section of an Ash body with no finish or base applied.
Here is an Ash body with only grain filler and nitro. Note how the nitro will mimic the substrate below.
Here is the Ash body with the catalyzed base sanded flat (Blue) and the nitro topcoat (Red). Note that the nitro will appear level and flat due to the level substrate.
Here are some common areas where the "wavy" effect will occur due to the rise and fall of the grain. (This body was shot with 3 coats of sealer and not sanded flat yet)
This is a great illustration of an Ash body that was finished with just "grain filler". Note the visible grain lines. If you do not like this look you will need the catalyzed base to level it out before the nitro is applied. (This is not my image however I thought it would be helpful)