Hammered Dulcimer design, construction, and unrelated stuff

Tuesday, January 15, 2019

How and Why of the New Finch Tops

Here is the why and how of the tongue and groove tops for the new Finch model hammered dulcimers. These are 2 photos of the tops before being glued to the frame, and you can easily see the tongue and groove joints.

Here is why we need to build them this way.  I built special humidity box to test a dulcimer we had built in the fall and kept it at 70-80% humidity for a couple weeks.  It did what it was supposed to do, the boards swelled all up and the joints narrowed but the dulcimer stayed in relatively good tune.  The first is a photo of it after 2 weeks in the "sauna"
You can see the joints are very narrow.  Below is the same dulcimer after 2 weeks of drying out in early winter in Iowa.
You can clearly see the difference.  This dulcimer is cherry which is pretty stable, but all wood moves like this, some much more.  The thing about this new design is the dulcimer stays in relatively good tune despite the changes.  It went 40 cents sharp in the sauna, and when it dried, it went back.  So 40 cents is the maximum, and it stays in fairly good tune with itself.  Below is a photo of a dulcimer we built at the height of summer with dew points in the 70s in Iowa, and no air conditioning in the shop.  We built it with the joints completely closed in July.  Now all 6 have opened up as you can see.  If this was an old fashioned one board top, there would be a couple nice cracks across it now.
We believe that this is how solid wood, fixed top hammered dulcimers should be built.  Other builders (as we have in the past) are making a mistake, and since this wasn't our idea to begin with, we have just been entrusted with it, we hereby give anybody that so desires the right to build their dulcimers this way.
Chris and Melanie Foss

Monday, August 7, 2017

Excluding moisture exchange from wood

Wood is hygroscopic meaning it wants to absorb or release moisture based on the humidity of the environment.  Wood reaches an equilibrium moisture content based on whatever the conditions are.  In a humid Iowa summer any wood can get close to 12% moisture content (MC) in a non air conditioned home.  In winter the same wood will pretty quickly drop to close to 6% MC in a normally heated home.   When wood absorbs or loses moisture it shrinks or swells across the grain but not along the grain.  It continues to do this as long as it exists as a piece of wood.  Different species swell or shrink different amounts, but all move to some degree.  We have a coffee table that I built of 150 year old reclaimed walnut from central Illinois.  The top is 2 ft. wide, and it will swell 3/8" from winter to summer, then go back when winter comes again.  This is quite a lot, and if a wood worker doesn't plan how to construct something based on this knowledge, it can lead to trouble. 

Even plywood is affected to a degree, but since it is layers with the grain going alternating directions, it is less affected. 

In order to build a hammered dulcimer that is completely tuning stable, we learned that moisture exchange has to be excluded from the wood.  It is the shrinking and swelling that throws a dulcimer out of tune, and it can happen fast if a dulcimer that is used to one environment is taken to another that is much different.  So we did a lot of research and experiments to find an appropriate coating.  Shellac doesn't work, nor does lacquer or varnish or polyurethane.  Surprisingly, according to the Forest Products Lab the most effective coating is melted parrafin wax!  It does work, but is quite a mess!  Boat builders epoxy also works, but needs to be at least 3 coats to be effective.  Other than that epoxy paint also works, but again needs to be at least 3 coats.

Sunday, October 18, 2015

On How to Properly Sand, and do a Hand Rubbed Finish

I really like Minwax Wipe On Poly.  I have been using it for years now as a sealer under shellac, but have recently discovered how to do a really nice hand rubbed finish with it.

The secret is in the sanding.  The finer the grit the surface is sanded to, the less poly it will absorb, and the quicker a gloss will develop.  So I currently sand starting at 100#, then 150# over the whole dulcimer.  The edges are sanded on a big edge sander, and the top and back are sanded with a stroke sander.  After that, I sand 150# with an air powered  random orbit sander followed by 180# on a different sander, and 220# on a third.  By this time the surface is feeling silky smooth.  Then I go over the whole dulcimer lengthwise to the grain by hand with 400# on a sanding block.

Then blow off the dust followed by wiping down with a tack cloth, then apply the first coat of Wipe On Poly as thinly as possible, but making sure the whole surface is covered.  I don't wipe off the excess, just make sure there isn't so much on as to drip or drool, then hang the dulcimer up to dry in the clean room.  After a couple hours the poly is cured enough to scuff sand with 220#, just enough to remove any dust motes, and make the surface smooth again, then blow off and wipe down with the tack cloth again.  The sparingly apply a second coat of Wipe On Poly and hang up to dry.

Next day I go over the whole surface very lightly with a worn out piece of 400# paper, just enough to get off any dust motes.  Then wax, and the finish is silky smooth!  I've been using the satin Poly, and it has a beautiful glow done this way.  I think if I wanted a higher gloss, after the 400#, finish sanding the wood with a quick once over with 600#, and in between coats of poly, scuff with 400# instead of the 220#.  The gloss Poly would also help.

Saturday, April 5, 2014

Amplifying Hammered Dulcimers

There are many different performance situations where you would want to amplify your hammered dulcimer.  If you are doing more than just jamming with friends, playing at home, or playing for more than a few people, then sound reinforcement is almost necessary.  There are several ways to do it.

Cheapest and easiest is to just point a standard dynamic mic like a Shure SM 57 or SM 58 at the dulcimer from above, and hook it to whatever sound system is available.  These work well in most situations, but if sound volumes are high, they can start to feed back.  Also, they aren't very sensitive, so the closer they are to the dulcimer the better, and sometimes they can get in the way.  The closer they are, the less they pick the other sounds going on in the room, so there's a happy spot somewhere above the treble bridge, coming in from the top, and just high enough to be out of the way.  If you have two of these mics, you can do a better job of picking up what you are doing pointing them at the dulcimer from either side.  The dynamic mics don't pick up everything that your dulcimer does, but are a pretty good choice for live performance with a band.  Sound techs usually understand them, and can get your sound to come through farily well.  Sometimes you can point a dynamic mic at the back of your dulcimer and get good sound, especially if there is a sound hole there, plus the mic will be out of the way, so it can be really close to the dulcimer which will exclude sound coming from other sources.  You might tell the sound tech to cut the highs back, and try boosting the midrange and possibly basss on your dulcimer.

There are several different onboard pickup systems that can be built in to your dulcimer, or installed after the fact.  They are all piezo type pickups which is the same thing installed in the street which senses your car is there when you stop at a light.  The pickups are small and light and can be adhered to many different points on your dulcimer.  Some folks just buy the piezo elements which are very cheap, and glue them to the under side of their soundboard in several different location, then wire them to a jack.  Drawbacks to these systems are they will need some type of active (battery powered) control box to run through before sending the signal on to the sound system.  The control boxes are readily available, since this is guitar technology, but can be quite expensive.  Then there is hammer noise to contend with which these systems will pick up strongly.  If the pick up elements are on the sound board, hammer noise can be very bad, and distracting.  They are also prone to feedback with the pick ups installed on the sound board.  This can be lessened by putting them on the rails or pin blocks of the dulcimer, but this also lessens how sensitive they are, so you have to turn the control box and possibly the sound board way up.  You'll never get rid of hammer noise completely with these systems.

There are a couple professional systems made for hammered dulcimer that work.  Schatten makes a two element system with the pick ups embedded in a silicone block to lessen the noise, and they sort of work.  They also sell a control box to go with the system, but it is pricey.

Another company called Pick Up The World makes a nice system which is complete based on two ribbon pick ups which I have found best to install one on the lower rail, and the other on the upper rail.  There is also a control box, and the system works quite well.  Their system is meant for retro fitting to the outside of the dulcimer, but then there are wires running everywhere, and things to get banged up.  It could be installed inside, but that would be best done while the dulcimer is under construction.  Then there's the cost, some where north of $500.00.  But if properly installed, it works pretty well, sounds surprisingly warm, and is quite feedback resistant.

So since I don't like the piezo systems, I stick with microphones, and have found what I believe to be the Holy Grail of hammered dulcimer mics.  The Audio Technica 2035 is a studio quality condenser mic at a very affordable price.  Condenser mics are more sensitive than dynamic mics, and the AT 2035 hears everything your dulcimer is producing very clearly.  Since there is more and better information being sent to the sound board, it can be adjusted, and you can get the sound you want out of the speakers.  Condenser mics need power fed to them from the sound system, it is called 48 volt phantom power.  Most sound systems have this capability, but free standing smaller amps do not, so small, cheap battery powered boxes are available to put in line between the mic and the amp to make the power.  You can sometimes pick them up for $20.00.  The AT 2035 new price is around $150.00, and will include the shock mount holder to put on the mic stand, and a bag for the mic.  The mic has a 10db pad switch, and a low cut switch, both of which I use when recording with mine.   The only drawback I can think of with this mic is it could be feedback sensitive in high sound volume situations, like a loud praise team at church.  For general use, though, I think it is the best.  When recording, two of these mics would be good, one on either side of the dulcimer from above.  They would be out of the way, and the sound will be very clear.  But then, of course, we are forced to be really good with our playing!

My friend Rick Thum told me about another mic which he uses, and it is good.  It is called DPA d:vote 4099G.  DPA stands for Danish Professional Audio.  The mic is very small, and used for all different sorts of instruments.  The G at the end stands for guitar, and indicates the type of holder they include with the mic system.  You attach the mic to the cool little holder, then attach that to the edge of your dulcimer and point the mic, which is directional, across the sound board.  It requires phantom sound, and is amazingly expensive, full retail is $600+.  The mic is really hot and faithfully picks up every nuance of what the dulcimer produces.  It doesn't color the sound at all, very transparent.  If you are prepared for that, it is wonderful.  Great for solo performance, and in a small group onstage.  I used one in church, and it was picking up the neighbors on either side, too until the sound guy figured out how to set it.  Then it worked well.

For recording videos in my little office, I have found the best setup is just two Shure SM58s.  Since the room is small and not well sound proofed, both the AT2035 and the DPA mic will pick up too much room noise and echo.  So the video setup is a Canon EOS Rebel T2i SLR camera which I bought for still photographs, but will also record video in full HD.  But the camera has an automatic gain control which is annoying.  If there isn't sound coming in, the AGC turns up the gain trying to pick up stuff, then turns it back down when something comes in.  It makes a rumble on the video.  So to take care of that, I have a Beachtek DXA SLR interface.  It will accept two mics, and record in stereo, but uses one channel to make a low hum which is below the threshold of hearing, but which the camera hears, and sets its gain accordingly, so the level going into the camera is uniform.  It works great.  I can plug two mics into the Beachtek but have found that it only records one side that way when set to kill the AGC, so I also have a little Mackie 1202 VLZ3 mixer.  Plug the two mics into that, then two outputs into the Beachtex, then into the camera, and I have stereo.  The mixer has tone controls, and also pan knobs, so I can set one mic to go into one side of the stereo, and the other into the other side.  I only need a little bass boost, and usually set the treble and mid at unity since I am trying to get the most accurate recorded representation of the actual sound I hear acoustically.  I also have a decent pair of headphones so I can hear exactly what is going into the camera as I am recording.

Thursday, May 23, 2013

Darkening Cherry With UV Light

At upwards of $12.00 per board foot for the good stuff, Walnut has gotten too expensive.  We used walnut for all our bridges and the rails of the Phoebe hammered dulcimers for 20 years.  Wood prices run in a cycle based on whether dark woods are in style, or light woods.  For the last 20 years, light furniture, light kitchens, pickled woods, white on white were the vogue, so walnut was affordable.  But now the trend has reversed.

So we had to find another wood that could contrast well with the birch top of the Phoebe, as well as sound good.  We had used cherry bridges many times, and it sounds great, but when new is sort of a bland salmon color, but darkens with time to a rich dark red which is beautiful.  Cherry is one of my all time favorite woods.  Trouble is we send out brand new dulcimers, but want them to look nice right away.  The bridges are unfinished, at our price point, a finish is out of the question, so the bridges need to just look good the way they are.

My wood dealer, Mark Hill of Hill Hardwoods in Iowa City, Iowa suggested that I might be able to darken cherry quickly with UV light.  He didn't know the particulars, but I was intrigued.  So I went to the internet, and there wasn't much out there, but lots of folks asking the same question I was.  I did find one mention that UVA was what you needed.

After much searching around, I found that a bug zapper bulb produces UVA.  UVB is what gives you a tan.  UVA is what causes cancer, so this is something to be very careful with.  Don't look at it without  eye protection.

Since the bridges are less than 20 inches long, I bought a 15 watt 18 inch bug zapper bulb on eBay, and got an 18 inch fluorescent fixture at Menard's.  The bulb was $15.00, and the fixture was $10.00.  I built a wood long enough to contain the bridges, mounted the fixture on the lid, and lined the whole thing with aluminum foil to keep the light bouncing around in there.  It works slick!  The lid fits tight, so no light escapes.   3 or 4 days in the box, and cherry gets quite a tan!  They look great on the dulcimers, and the position marks show up nicely.  It really is too cool!

Monday, March 4, 2013

Shellac Finishing Small Parts

I have to thank the guys at Woodsmith on PBS for this great technique.  It needs to be shared with the world.

Since shellac is a universal sealer, and will stick to anything, you can put it right on over wet oil, and it will seal the oil in.  Pretty amazing.  Hand rubbed oil finishes are the deepest and most beautiful, but take a lot of time.  But with shellac in the mix, you can do a complete finish in an hour or so.

First, rub on boiled linseed oil or whatever oil finish you want to use.  Wipe off the excess.  The oil really brings out the color and grain of the wood better than any other finish.  Immediately you can pad on shellac, and it dries right up, and seals the oil in.  Pad on as much shellac as you want to get the gloss you want, or switch to some other top coat, and you're done.  The oil will go ahead and cure under the shellac over the next few days, but you can use your item right away, it is done.  I finished one of my mountain dulcimers in an hour with 1) boiled linseed oil, 2) shellac padded on until I got tired of it, 3) wax.  It looks great!

This technique is the best way to finish dulcimer hammers, or any small item.  The only tools needed are some clean rags.

Sunday, December 23, 2012

Spraying Shellac Revisited

I have been spraying shellac in production finishing of our hammered dulcimers for a year now, and have come up with a few more tricks, so thought I'd update.  Read the former post on the same topic, this is additional material to that.

I have found that shellac sprays best if it is mixed at an EXACT one pound cut.  This is pretty easy to do.  I have a jar that I dissolve the flakes in that is something less than one gallon, so just dump the flakes in, fill with alcohol, and stir several times the first day.  If I stir well a couple times within the first hour, the flakes will all be dissolved by the next day.  Then I filter the mix into a gallon jug, and top off with alcohol to get the right mix.  This is probably a little stronger than a one pound cut, but works best for me.

Jugs:  glass is best.  Milk jugs work, but are thin, and the shellac can actually find a weak spot, and eat through, and leak.  But you won't lose much, because the shellac dries, and is self healing.  I found a much heavier plastic jug that vinegar came in, and it has been working very well.

Since I had sprayed lacquer for so long, it took me quite a while to get the feel for the shellac.  I was putting it on too heavy.  So, one pound cut, spray light, and move fast.  Shellac goes on different than lacquer, it does not need to wet and flow out, so you wind up moving much faster than you'd think.  I am using about half the material I was, and getting a much better finish.  The surface may look a little pebbly, but give it a minute, and it will settle down, and gloss.  Go especially light on the first couple coats, which are your seal coats.  Much less grain raising that way.

Color:  I have gone to using just the Blond flakes that I still get from shellcshack.com.  They give just a little warm glow to the finish.  I no longer mix colors, but this is still a good trick for special finishes.  But production finishing, just the Blond.

Gun cleaning:  I clean after each time I spray, never leaving shellac sitting in the gun.  By cleaning, I mean, pour the remaining material back in the jug.  Put a little straight alcohol in the gun, shake it to get the alcohol all through the cup, then spray a little of the alcohol.  Pour the remaining alcohol into a separate container that I label "Gun Rinse".  Then pour a little more fresh alcohol in the cup, shake, then spray.  You can let the gun sit as long as you like now.  When getting ready to spray again, pour the alcohol in the cup into the gun rinse can.  The gun rinse alcohol can be used in mixing up the next batch of flakes, so you don't waste any of it.  It is a good idea to take your gun apart a couple times a year, and soak and thoroughly clean all the parts.

Shellac is harder, and more durable than lacquer.  I have switched to it completely.  I don't spray lacquer at all now.  So much better!  It is also more beautiful than lacquer.  I still use the Minwax Wipe On Poly as a sealer, as described in the former post.  It works great, and helps the shellac build faster.  I just wipe it on straight, and let sit overnight.  Then scuff lightly with 220 grit paper on a sanding block. For scuffing in between coats of shellac, I have found 400 grit best, wrap 1/4 sheet around a rubber sanding block, and move your hand slowly and with very light pressure, basically just the weight of the block and your hand.  Don't press down.  If you do it right, the paper won't load at all, but if you move your hand too fast, or press down too much you will generate heat, and the dust will load the paper.  I have a piece of carpet on my sanding bench, so just wipe the paper on that to get the dust off.  With a smooth couple of seal coats, I don't need to do much sanding, just go over it lightly to get the dust motes off.  If there is a rough spot, I can do more sanding there to get it smooth.

Final polish:  With the much better job of laying the finish on that I have developed, I don't need to rub out.  The gloss is there, just like I want.  So for the top of the dulcimer, I just pass over it VERY lightly with a worn out piece of 400 grit paper to remove any dust motes.  You can't see that I have done this, and it doesn't affect the gloss at all.  For the back and sides, I still love the feel and look of wax, so I sand a little better, then wax.  I probably wouldn't need to wax, just go over the whole dulcimer lightly with the worn out 400 grit.  I just really like the feel of the wax.  These are by far the best finishes I have done in over 20 years.

I have gotten good enough with my move fast, spray light technique that I have been able to drop the use of the bed of nails on the turntable, and go back to suspending the hammered dulcimer bodies from a string hanging from the ceiling of my spray room.  I worked this way for 20 years spraying lacquer, and it is much faster.  I can spray all around the body at once.  I do six at a time.  To do the whole finish on six dulcimer bodies used to require a little less than a gallon of lacquer mix.  Two quarts of sealer mix, and 2 quarts of semigloss mix.  With my move fast, spray light technique, I am down to just over a quart of 1 pound cut shellac to do the same job, and the finish is better.  So about 1/3 of the material, and shellac works out to be cheaper than lacquer.

So; shellac is harder, more durable, and better looking than lacquer.  It takes a little longer to apply, but the results are worth it.  I am using a lot less material than I would lacquer, and I believe this has translated into cheaper.  Shellac is safer, I don't need to keep 5 gallon buckets of hazardous materials around.  It is safer for the environment, safer for me.  It is also safer for customers since there are no chemical sensitivity issues.  It is better for the economy since I am not supporting a large chemical company, just small businesses like shellacshack.com, and the guys in India that produce the flakes.  It is a win/win/win/win situation.  What isn't to like here?

In going over these posts I realize I have left out something big.  Spraying shellac can be dangerous.  An aerosol mixture of alcohol is explosive.  Don't try it in your basement.  You either need to be outside in the open air, or you need explosion proof facilities inside.  There are two types: A spray booth, and a spray room.  A spray booth is a 3 sided box with a very large explosion proof exhaust fan in the back, and over spray arrestors to filter the air before it goes through the fan.  Large spray booths are where body shops paint your car, and they require a LOT of air to keep any of the aerosol spray mix from escaping into the shop.  A spray room uses a much smaller fan, but takes up a large foot print in your shop.  To be up to code, a spray room needs to be covered on the inside with 5/8" drywall, the lights need to be explosion proof, have an explosion proof fan to exhaust outside, and all electric switches need to be on the outside of the room.  This is what I have, and with the amount of spraying I do, it has been one of my best investments.