Question on Sanding Sealer

[acaron41120]

Quick question on using sanding sealer. I have used it many times on ships whose hulls are painted with great success. But I'm unsure if I should use sanding sealer if I am staining the wood. I'm afraid that if I used sanding sealer then stained the wood, the stain would NOT soak into the wood s it should. Am I correct in my thinking?

[toms10]

Hi Allen,

Yes you are correct. You need to have bare wood for the stain to soak into the wood. You can seal it afterwards with urethane or shellac if so desired. There is a product you can apply to wood before staining called a leveler. It is a watery substance that is intended to help level out the color when applied to wood with coarse or varying grain texture on large surfaces. I don’t think it is necessary with the types of wood we use and relatively small surface areas. 
Tom

[Jaager]

What do you mean by "sanding sealer"?

A stain or dye should be used on raw wood.

A true sand-n-seal product is targeted at open pore wood.  This group is generally nut wood  Oak, Hickory, Willow, Pecan, Ash, Walnut - species of wood that are either not really appropriate for our uses if the wood is to be left natural.  They will work as well as any if painted.  But the open pores will need to be filled first. 

This is what a old style sand-n-seal is for.  It was or is a thick lacquer with clear when dry fine solids meant to fill the pores.

 

The wood that we should be using is closed pore and tight grained.  There are no pores that need filling and a clear top coat that is thick is best avoided.

 

If  a primer is what you mean,  there are much better products than a lacquer with pumice or a similar solid.

The gold standard is half saturated shellac.  Cut premixed 1:1 with denatured alcohol (shellac thinner/ ethanol with an emetic to avoid taxes).

You can also use 1:1 diluted Tung oil (pure - not Homer's or similar) or 1:1 boiled Linseed oil.  In these cases mineral spirits is the usual diluent.

Shellac is ready to overcoat as soon as the alcohol evaporates.  The oils will need time for polymerization before they are overcoated. 

All in all - shellac is just too convenient unless you are not in a hurry.

 

If you use a dye - and for us - at this point in knowledge - I think that alcohol based dye us best - water based dye will swell the wood - our models will not sit outside in the sun and the surface is too small for any additional depth by water to be seen.  Dye - then primer.

If you use a traditional stain - which is really a diluted wood color shade paint - shellac would go first.  The primer will make the stain/paint go farther.

[AON]

Re: your first posting

As per the second posting - Yes you are correct.

[Bob Cleek]

13 hours ago, Jaager said:

What do you mean by "sanding sealer"?

I was thinking the same thing. I agree completely with Jaager's sage advice. We are kindred spirits when it comes to using premixed canned 2 or 3 pound cut clear shellac for sealing wood, cementing knots, shaping line into coils and catenaries, making flags look like they are flying, shaping cardstock, and when thickened, even as an adhesive under certain circumstances. (In fact, they also use thinned shellac in food processing to make jellybeans and apples and citrus fruit shiny.) I don't think we are necessarily in the majority of modelers who use shellac for so many things, but I'd expect many of the "geriatric set" do, having discovered that nobody's really come up with a better material to use for any and all of these purposes. And, as an additional benefit, shellac is easily removed (and rigging knots requiring adjustment easily untied) by simply wiping it off with an alcohol-soaked cotton swab or piece of cloth, since the hardened shellac immediately dissolves in contact with alcohol, the all-purpose solvent used to thicken and thin shellac and easily clean up after use. 

 

I think that a "sanding sealer" is somewhat of an oxymoron, given that there isn't much point in sealing a surface if you are going to sand it, since that sanding is going to remove some, if not all, of the sealer which doesn't soak into any wood species very deeply (and practically not at all on the flat of the grain.) The only application I can think of which calls for sealing a surface before sanding, and then only at the very end of the surface preparation exercise, is to "harden" a soft wood such as basswood at the last step and apply a very fine light sanding to remove the "fuzz" from the surface of woods that tend to "fuzz" when sanded. Thinned shellac, which penetrates the word surface as far as anything does, and that's not much, binds the fine wood fibers together and permits a fine sanding that doesn't raise "fuzz." In doing so, you have to be careful not to sand through the sealer coat to bare wood. Not only would this wood be unsealed if the sealer-permeated wood "crust" is sanded through, but also, subsequent coats of paint will soak into the bare wood, resulting in a painted surface which betrays this fact. In the case of gloss finishes, the unsealed (unprimed) spots will show as flat (matte), instead of gloss to one degree or another. The inexperienced will often apply additional finish paint before the first coat is uniformly dry in an attempt to "gloss up" such flat spots and, as more experienced painters know from hard experience, "going over" anything applied wet before it dries thoroughly rarely comes to any good end. 

 

To cover a base that may have been missed, I realize that many, rightly or wrongly, refer to "plastering" a piece (usually a hull) with, literally, plaster or drywall "mud," Bondo, (tm)" epoxy putty, or "fairing paste" made up of epoxy resin and various proprietary "sanding (or "fairing," or "surfacing") additives (e.g., "micro balloons.") after assembly of the wooden substrate and then "hogging off" as much "surfacing" material as is necessary to fair the piece and leave the remainder of the surfacing material to fill the cracks, craters, and even canyons on the original as-built surface. In a perfect world, everybody's planking jobs would look like those of we-know-who here on MSW, but for most of us, that's not going to happen in our lifetimes and "filling", or "fairing" is a routine task which is of great value in covering a multitude of errors. It's essential to obtaining a "smooth-as-a-baby's-bottom" finish if open grain woods are used. (All those whose drill instructor used a different simile to describe for this desired level of smoothness, raise your hands. ) There's a use for shellac here, as well.

 

There are many products marketed for filling grain and minor surface imperfections. They are usually overpriced and of varying degrees of usefulness. There is a very simple traditional and certainly archival method of filling minor surface imperfections using shellac. In the manner similar to "French polishing," when a surface is sanded sufficiently fair, it can thereafter be rubbed with a felt and/or cloth pad containing an oil (e.g. linseed oil, raw or boiled,) and pumice (powdered volcanic glass,) This process will cause the pumice to abrade the sealed shellack-sealed surface while at the same time filling the open pores of the wood grain with a slurry of shellac sealer and pumice, which being glass, becomes transparent. Repeating this process as with French polishing, will result in a perfectly smooth surface. If one wishes, the same can be done using fine grit "wet or dry" sandpaper. See: Wikipedia on "French polish" for an explanation of how it's done. It isn't rocket science and the learning curve is practically a flat line, but, unfortuntely, it's not about skill as much as it is perseverance.  French polish - Wikipedia There's also a ton of YouTube videos on it. It's a good, easy to learn skill to have in your tool box.

 

If we are talking about a lot of filling needing to be done, sealing with thinned shellac may be advisable before the fairing material is applied. The shellac provides a stable base that is more effective for many putties and plasters adhering to than bare wood.  This initial sealing before filling is highly advisable with "wet" materials that contain water which will more readily be absorbed by bare wood which will result in a "cure" of the surfacing material and a "damp" subsurface where the wood and plaster or other surfacing material meet due to water absorption from the surfacing material. This may result in shrinkage of the surfacing material requiring multiple applications, weak adhesion, especially on thickly applied areas, or even mold and other unwanted issues. Surfacing materials with resinous binders such as Bondo and epoxy adhesive resin with "sanding additives," are not prone to having their solvents "sucked out of them" by their contact with bare wood, as occurs with the water in surfacing materials containing water. One parenthetical caveat: Many are familiar with automotive body and fender "fillers," such as Bondo. Bondo and however many of its similarly compounded competitors is designed to adhere to metal, not wood regardless how well it might do so in any event, or whatever the instructions on the can may state or imply. Bondo is hygroscopic. This means that when water "seeks its lowest level," Bondo is part of that equation. "Bondo" attracts and holds, which is to say "absorbs," water from the air. If the moisture content of cured "Bondo" is lower than the ambient air, the "Bondo" will absorb the difference until equilibrium is reached between the drier "Bondo" and humid air. Similarly, if "Bondo" is applied to wood, and the moisture content of the wood is lower than that of the Bondo," the wood will suck the moisture out of the "Bondo" until the wood's moisture content reaches equilibrium with the "Bondo" and, in turn, the ambient air.  Now, for models that will live in glass cases in cozy, climate-controlled homes, there may be little point in worrying about this bit of physics (or is it chemistry, or both?) There may just not be that much moisture involved in the environment in which the model will exist to cause any problem at all. However, in the real-life full-scale world of wooden ships and boats, Bondo and other polyester resins are frowned upon because in the marine environment there is certainly enough ambient moisture around on a regular basis to cause the wood beneath Bondo patches to become wet, soft, and infected with fungal decay in such a way that the Bondo no longer holds very aggressively to the wood and, eventually, the wood decays.

 

It is not likely many of our models will survive much longer than any life-in-being on the day we die. We will all eventually become that grandparent or great-grandparent or other relative who "died before I was born" and who "I never knew." Unless we were royalty, National Enquirer level celebrities, or left them a large trust fund with a specific endowment to fund the preservation of our model collections, the majority of our descendants who are born after we have died aren't going to be the slightest bit interested in preserving our handiwork. (Indeed, I personally know at least one modeler's spouse who's highly likely to dispose of all her late husband's "damned boat junk" as soon as the opportunity presents itself! ) However, maybe... just maybe, one of our models survives, by virtue or happenstance, and if that happens, I've come to conclude that using state of the art archival materials and practices whenever possible is a good thing because, if and when that ever happens, it may well be in large measure because it has simply lasted longer than the rest. 

 

If you sense a bit of the Luddite in all this, I'll plead guilty. Since this is all "mature technology," I have to say it's all been thoroughly "Beta-tested." Using lasting materials makes sense because so much time is invested in a model that lasting materials are well-warranted. In closing, let me add, "avoid water-based materials. The water soaks into the wood and it raises the grain no matter what you do. Always seal with a good sealer. Shellac is one of the best natural, non-toxic sealers around and one of the less expensive. Stick to tubed artist's oils, linseed oil, turpentine, and Japan drier to mix your own colors or at least to condition unmixed colors. You'll save money and your work will endure if at all possible. Build using safe, "organic" materials and avoid becoming too dependent upon the synthetic chemical industry. 

Edited January 21 by Bob Cleek

[acaron41120]

Thanks everyone. I will continue on using the method I have been using as it turns out it was the correct method. I usually sand and fill using the sawdust from sanding with a mixture of the sawdust and glue which works much better than sanding down the commercial fillers that just don't seam to sand down enough. Before painting, I use a tack cloth and then add one light coat of sealer and follow up with the color of choice for my particular ship. For Mayflower, and the Golden Hind I will stain the hull with a quality stain and then paint from the waterline down flat white.

Again thanks everyone for your help.

Edited January 22 by acaron41120