Sanding and Finish on a Laminated Blank

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Ed Weingarden

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I have in mind to make a laminated blank consisting of acrylic, aluminum and wood. When I've used acrylic by itself, I wet sand and don't apply any finish. With my proposed blank having wood, I don't think I can wet sand. Any suggestions as to how to sand the blank. With respect to a finish, I usually use CA. Will there be any problems with the CA adhering to the acrylic? Thanks.
 
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Since your using aluminum you'll need to forgo any sanding. That aluminum dust will ruin your efforts.
 
My experience when sanding wood with aluminum inlays has been that as long as I apply a coat of sanding sealer first, I have not had a problem with the aluminum dust.
 
IF you want a smooth finish before applying CA, use a very finely sharpened scraper or radiused carbide insert, or a skew layer flat on the post. It will smooth the finish well without the need for sanding. CA can be applied over that.
 
This question has come up many times here on the forum but recently come up again about 3 or 4 different times but asked in different ways. I will again give my thoughts and what I have found over the years being that I like to do many segmented blanks and using various materials. One thing I did very shortly after I learned to use a lathe and that was to try to learn the process of using a skew. I often heard and now believe it is the one turning tool that can do just about any cutting stroke if mastered. Now I have not mastered it but have become pretty efficient with it. One area I found its use to stand out is dealing with this question so often. I do not sand my segmented blanks. I use a round carbide cutter to get me down to close to finish state in size and finish. I then take the skew and finish the turning with the angle of the skew at its almost nil cutting stage. To do this I lay the cutting edge on the shoulder of skew and gently raise it till is just starts cutting and slide it across the blank and with a sharp skew it leaves an unbelievable flat and clean finish. If I need to take out any hills or valleys I will lay it in a scraping motion and level off. But what I found it does not leave that perfect feel if left alone so I go back to cutting.

Now I am not a believer in sanding sealer or CA use to prevent bleedover and the reason is because I have seen where the liquid no matter what is will draw color out of certain woods such as Paduk and contaminate surrounding woods such as soft woods like maple. Been there so stopped using it and never looked back. With CA you have to wipe it on and again the transfer of color is possible. You may get away with it on certain woods. If you are going to use a sealer I would use a spray such as dewaxed shellac. Again no guarantees. But a fine mist for the first coat should do well. Do not flood it on. Then you can continue with coats as you get close to finish state. Good luck. I have plenty examples which I have shown here before so will not clutter page up with them again.

Have to edit this because I just saw other part of question about CA use. Yes CA will stick to acrylic and metals. It is used alot with those combo blanks that members make with punky woods and casting resins. Also with segmented GISI blanks people make.
 
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One issue with sanding& finishing is that the finish must adhere to the materials used in the work. If you sand or MM to high grit levels you reduce the ability of the finish to key / adhere to the surface.

When the work is built up from materials with differing properties i.e. wood/s, acrylic, epoxy / polyester resins, stone, Corian, metals it becomes a trial to experiment with the combination of 'off the tool' finish or finishing sanding grit, choice of finish and application method that works best overall with all of the materials. Sometimes we simply cannot achieve that 'perfect finish.'
 
mobyturns said:
One issue with sanding& finishing is that the finish must adhere to the materials used in the work. If you sand or MM to high grit levels you reduce the ability of the finish to key / adhere to the surface.
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In my experience, it depends upon the material. I have paint on one of our glass windows that has been there 30 years. Smooth wood is not the problem, it is the moisture from humidity changes along with temperatures changes that eventually makes finishes let go and curl up.As to CA as a finish, CA has been used to adhere mirrors to the windshield and they have held for 50 years in many cases. CA as a finish "can" do the same with wood finished to the same level and then totally sealed.

I grew up around older house construction relatives who said the same thing but they could never tell me why the same paint will adhere to glass pains in the sun for ages. Its the humidity/moisture under that loosens it,
 
Hank, I agree with your statements about changes in the moisture content in wood affecting the durability of a film finish such as CA. The surface roughness and preparation has a significant bearing on the finish adhesion, and the finish 'chemical' compatibility with the substrate materials also determines bond strength, durability & longevity.

Yes, oil based paints adhere well to glass, acrylic water based paints not so well. CA does not do so well on some woods.
 
Man you can open a whole detailed explanation of finishes on different materials as well as types of finishes used. Bob Flexner has great reading material out there. The principle about finishes locking into a keyed substrate is true to some extent. Also uv as well as heat, cold and humidity can effect all finishes no matter how well the finish is applied. As with paints, finishes weather clear or colored have binders and resins added for adhesion purposes. This is what makes them stick to surfaces. Of course they all use different amounts and kinds depending on the type of paint or finish. Not all acrylic paints or finishes are equal as well as not all waterbased are either. Same goes for CA. So to say with certainty that a finish or CA will adhere to certain materials is tough to call. Other factors such as prep work is a factor also.

Getting this topic back on track for the OP, the question is twofold. My explanation above will explain the CA bonding to acrylics and metals stands with the notion not all CA's work and hold well. I prefer Satelite City CA. Have had no peeling or cracking when doing what OP is asking.

To the other question about sanding combination of materials I must add to my recent post that all materials do not sand the same because of their hardness. So yes you can wet sand acrylic and metals but acrylics are softer and could sand faster and leave ridges when doing that. Same goes for sanding wood and acrylic. One way I get around this is to alway use a flat block of wood and sand the blank that way with sandpaper wrapped around it. I never finger sand because your finger will follow all ridges. This always applies to sanding larger projects too. Best to use a sanding block to sand evenly. Hope this helps.
 
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