Sandpaper. Use. It.

[JerseyCity Frankie]

I debated writing this but then thought it couldn't hurt: sandpaper. Use it! I don't want to name and shame anyone, but there is a huge proportion of finished models displayed on MSW on which the detailed photos of deck fittings or mast details show a lack of adequate sanding and surface prep. It looks like a lot of builders punch out the laser cut parts and incorporate them directly into the model without sanding to an adequate degree. I KNOW that close up photography of small parts reveals flaws not visible to the naked eye but some of the model photos I see show that a lot of small wooden parts are going onto models without enough sanding taking place, the surfaces are often covered in irregular globs bumps and spikes.

since most kit models are basswood, it helps to recognize that the biggest drawback of basswood is it's fuzzyness. In other respects it's a great material but at the near-microscopic level fibers at the edges are very stringy, they don't break off neatly at the surface of the wood but cling on randomly as fuzz. Paint or varnish going on over this fuzz only serves to make the fuzz bolder and stick out in hardened spikes and that's what I'm looking at in these detail photos I'm seeing. I'm going to make another plug for the use of a Sanding Sealer. Available in any hardwear store, one can should last your entire modeling career. I use a water based Minwax Sanding Sealer. It paints on like thin acrylic paint, completely transparent. When dry it has the effect of darkening the wood just a bit. Is that so bad? The surface you get has hardened and feels shellacked. When you go over it with fine sandpaper those annoying stringy grainy fibers break right off at the surface in a way that reminds you of those old animated cross sectional shaving razor commercials in which each hair is lifted and cut perfectly at its base. You get a smooth surface where the grain is still visible but not in the form of huge peaks and deep valleys, a surface that can withstand the scrutiny of close-up miniature photography.

[Srodbro]

Would the sealer affect or be affected by CA or other adhesives?

[reklein]

I think the sealer would improve the use of CA as the wood is sealed and the CA won't soak in so much. If you apply CA to end grain often it will just soak in and leave no glue on the surface so you have to reapply the glue.

[rcmdrvr]

Can you stain over sanding sealer.

[Canute]

No, since you've just sealed the wood. I'd recommend staining first.

[reklein]

I disagree with Canute. One of the reasons for sealing is to prevent the wood from taking stain color unevenly. Secially in the case of porous woods such and oak and pine. Pine for instance if left unsealed will be blotchy od where theres knots will not take stain at all. Also you need to seal before any paint or lines are put on as your paint will run along the grain of the wood and lose its sharpness.

[Canute]

Bill, you're right with those woods. I've been tunnel vision on small scale models and  basswood. I use a conditioner on the basswood before staining, but that's not a sanding sealer. Thanks.

[vossiewulf]

Not sure what you guys are talking about, sanding sealer is just a standard clear lacquer/varnish/poly with a high percentage of solids. As such, once applied, the strength of any glue bond you get is (depending on finish thickness) mostly or entirely limited to the strength of the finish's adherence to the wood, which is always going to be MUCH less than that of glue bonding with wood. In some cases with thin CA and a light coat of sealer you'll still get a semi-strong bond as the glue sinks into still-open grain and that creates a mechanical hold, but it's still not going to be as strong as it should be bonding with plain wood.

 

I almost never do that, I will remove any finish including sanding sealer from a surface before gluing.

 

Anyone who wants to really understand what all these finishes really are and the basic chemistry of how they work should read Understanding Wood Finishing: How to Select and Apply the Right Finish, it's about the most advanced finishing book I've found in terms of explaining all the source materials of finishes and how/why they work the way they do. You'll learn that much of what you think you know is wrong and that much of what manufacturers say about their finishes is complete nonsense, but other info on the can that you're not really paying attention to now is very important and will tell you exactly how that finish will behave.

 

It's from American Woodworker which I normally don't associate with highly technical woodworking (like Fine Woodworking) but this really is the best book I've found, and I probably have 15 or 20 books on different types of finishing.

[reklein]

One can remove any finish before gluing and you can also perforate a sealed  surface with a pin, that is poke a whole bunch of little holes in the wood to allow whatever adhesive to penerate. Used to do that on oil soaked R/C model airplane wood to get a few more flights out of the plane.

[Chuck Seiler]

Vossie,

 

    Thanks for the tip on the book.  Finishing has been a weak area with me.  In some cases I prefer to paint a piece before installing it to ensure a crisp paint line, or lack of over paint.  Similarly, paint or stain a section before installing moulding.  The issue has always been to seal or not seal. 

 

    I have painted with some success using a method outlined by Chuck and others.  However, I only paint small areas.  I either stain or leave natural the bulk of the model.  I usually avoid sanding sealer due to fear that it will screw up efforts to stain.  Perhaps I should experiment.