Starting varnish experiments with a new UV cabinet - any recommendations?

[Geigenbauer]

Hi everyone,

I’m an amateur violinist and maker. I am currently trying to pick both playing and making up where I left it almost 12 years ago. Getting all the tools out again and starting on a new instrument is a lot of fun but still as difficult as it was back then. However, having YouTube and forums like this one is sure a great help for an amateur. Many thanks to all that post here.

While I continue to work on the instrument, I would like to start the first varnish experiments. Varnishing was a major problem on my first two instruments, and I would like to be better prepared this time.

I just finished building a new UV cabinet (pictures attached) equipped with eight 40W GE F40BL (UVA 350-365 nanometer) tubes. I included a programmable switch for the lights, an air filter and a thermostat-controlled fan (AC Infinity AIRPLATE T7). I hope this setup will work. I built the cabinet large enough for a cello (my wife plays cello).

Here are a few things I plan to try out first. I would greatly appreciate additional recommendations & suggestions:

-       How many days are needed for a maximum tanning effect?

-       Do 1,3 or 5 coats of gelatin have an effect on tanning?

-       Testing 0,1,3,5 coats of gelatin with different ground coats (thick rosin oil, self-made varnish)

-       Trying fine pumice mixed with rosin oil or varnish as ground coat over gelatin

I will try to make my own amber varnish. Last time I did this I fused the amber myself, but this time bought the amber colophony from Kremer. Does anyone have experience with this product? I am planning to start with a 1:1 ratio of amber colophony in boiled linseed or walnut oil. Any recommendations for one vs the other?

Many thanks in advance!

 

 

[scordatura]

Nice looking cabinet!

[barnesviolins]

13 hours ago, scordatura said:

Nice looking cabinet!

DITTO!

I'd be curious what temperature it runs with all the lights on.

Dorian

[Michael.N.]

Watch the RH,  8 x 40 W is a lot of heat for a confined space. I get away with a single 40 w light in a cabinet that is probably a bit less than half that size. I still use a baby bottle warmer to maintain humidity. 

[David Burgess]

Nice looking light box! I made the walls on mine out of aluminum sheet screwed to a skeleton frame, and mounted the ballasts outside the box to keep the interior heat down. I also use only 4 tubes, which seems to work fine for varnish drying, but may be slower for tanning (which I don't do, so don't have much experience with).

I'd recommend lining the top and bottom with aluminum foil as well, so the varnish on the ends of a cello doesn't dry much more slowly than the rest of the instrument.

And I'll put added emphasis on what Michael N. said about monitoring the relative humidity inside the box. It will fall as the temperature rises. People have had instruments crack due to the dryness in their light boxes.

[Don Noon]

On 9/14/2019 at 3:11 PM, Geigenbauer said:

I will try to make my own amber varnish. Last time I did this I fused the amber myself, but this time bought the amber colophony from Kremer. Does anyone have experience with this product?

In reading this, it is not clear that you understand the difference between fused amber and amber colophony.  Although Kremer doesn't have much in the description, I am 99.44% sure that it is just a dark-colored rosin.  You can probably search thru the semi-inifite number of posts about making rosin (or colophony) varnish here on MN for information, although the dark Kremer might behave slightly differently.

[Michael_Molnar]

1 hour ago, Don Noon said:

In reading this, it is not clear that you understand the difference between fused amber and amber colophony.  Although Kremer doesn't have much in the description, I am 99.44% sure that it is just a dark-colored rosin.  You can probably search thru the semi-inifite number of posts about making rosin (or colophony) varnish here on MN for information, although the dark Kremer might behave slightly differently.

It's not fused amber but an amber colored colophony similar to dark FF rosin. It is brittle  enforce cooking according to Kremer. I have no experience with it. 

[Michael_Molnar]

This is a lovely cabinet. I suggest adding air vents, (fan), thermometer, and hygrometer (for relative humidity readings) as David recommended.

[Jim Bress]

1 minute ago, Michael_Molnar said:

It's not fused amber but an amber colored colophony similar to dark FF rosin. It is brittle  enforce cooking according to Kremer. I have no experience with it. 

I gave a small bag of the "Russian" stuff to Don L.  I don't know if he ever experimented with it.

[JacksonMaberry]

From Varnish Making and Kindred Industries, Vol. II - Livache and MacIntosh, on Amber:

Fusibility. — The melting-point of amber varies from 287 to 290° C. (about 548'6-554° F.). When heated it decomposes and gives off a pleasant aromatic smell, fuses and burns with a bright flame. When gradually heated in linseed oil to the " boiling" point of the latter, and kept at that temperature for twenty hours, it becomes soft, pliable and ductile, but does not melt nor decompose. It must, however, be cooled slowly in the oil, or it becomes as brittle as glass. Opaque spots may in this manner be rendered translucent, and the amber moulded to any form, and pieces can even be cemented together. Amber is repaired by smearing the fracture with linseed oil, pressing the pieces energetically together and heating them by holding them over a charcoal fire. Amber may be dyed by inserting it in linseed oil coloured by alkanet root, dragon's-blood, alizarine, purpurine or coal-tar dyes. The heat is maintained at 190-200 °C (374-392° F.) for a few minutes and then allowing it to cool slowly in the oil. Heated in a fluorescent oil, amber also becomes fluorescent. 

Amber-Oil Varnishes. — These are the hardest varnishes known, but on the other hand they are wanting in elasticity ; they are thus used to cover surfaces little subject to vibration or to bending motion. They answer remarkably well for such comparatively inflexible sub stances as glass. Owing to the high temperature at which amber melts, and also to the different pieces not melting at the same temperature, amber-oil varnishes are generally dark in colour. The relative proportions of the ingredients usually taken are: Fused amber, 10 lb. ; boiled linseed oil, 8 to 30 lb. ; spirits of turpentine, 10 to 25 lb. The quantity of linseed oil varies from 8 lb. if hardness be required to 30 lb. when elasticity is a desideratum. The quantity of spirits of turpentine is regulated by the degree of fluidity. If hard ness and transparency and a quick-drying varnish be required in pre ference to elasticity, the amber is largely increased, and a very volatile solvent such as benzene is employed, say : Fused amber, 10 lb. ; lin seed oil, 2| lb. ; benzene, 5 lb. Finally, it is often advantageous whilst taking advantage of the hardness of amber with the view of in creasing its elasticity without very appreciably impairing its hardness to replace a part of the amber by copal, say : Fused amber and copal equal parts, 1 lb. ; boiled linseed oil, 1 lb. ; spirits of turpentine, 2 lb. The result is a hard durable elastic varnish. In cheaper varnishes the whole of the copal in the above may be replaced by carefully selected higher grade rosin. 

 

There is a very expansive chapter in this book that describes running Amber and making varnish with it. The source material is from the late 19th century, expanded and published in the early 20th. 

[Geigenbauer]

Many thanks for all the comments and suggestions thus far. I will respond step by step over the next few days.

I ordered a combined hygrometer/thermometer and will share temperature and humidity readings asap. The cabinet is equipped with a double fan, temperature sensor and control unit. I bought the whole set online. Because the fans are blowing the warm inside air to the outside, I installed an air filter at the bottom of the cabinet to prevent dust from being drawn into the cabinet. I am not sure how well this will work because the cabinet doors are not airtight and there will for sure be some leakage.

Below are a few pictures of the fans and control unit.

[Geigenbauer]

I would also like to provide some additional information about the “amber colophony” from Kremer (#60205). I purchased this material because of the information provided on the German Kremer webpage.

Here is what is stated on their webpage including a rough translation:

“Bernstein Kolophonium” (#60205)

Altbestand aus einer ehemaligen Bernstein-Lackherstellung in Russland. Dieses braune, brüchige Harz wird zur Bernsteinlackherstellung verwendet und ist, ähnlich wie Kolophonium, mit Leinöl verkocht für die Geigenlackherstellung verwendbar. Nur begrenzt lieferbar.

Old material from former amber-varnish manufacturing in Russia. This brown and brittle resin is used for the production of amber-varnish and can (similar to colophony) be cooked with linseed oil to make violin varnish. Limited stock.

https://www.kremer-pigmente.com/de/bernstein-kolophonium-60205.html

Edited September 18, 2019 by Geigenbauer

[Julian Cossmann Cooke]

On 9/14/2019 at 5:11 PM, Geigenbauer said:

 

Hi everyone,

I’m an amateur violinist and maker. I am currently trying to pick both playing and making up where I left it almost 12 years ago. Getting all the tools out again and starting on a new instrument is a lot of fun but still as difficult as it was back then. However, having YouTube and forums like this one is sure a great help for an amateur. Many thanks to all that post here.

While I continue to work on the instrument, I would like to start the first varnish experiments. Varnishing was a major problem on my first two instruments, and I would like to be better prepared this time.

I just finished building a new UV cabinet (pictures attached) equipped with eight 40W GE F40BL (UVA 350-365 nanometer) tubes. I included a programmable switch for the lights, an air filter and a thermostat-controlled fan (AC Infinity AIRPLATE T7). I hope this setup will work. I built the cabinet large enough for a cello (my wife plays cello).

Here are a few things I plan to try out first. I would greatly appreciate additional recommendations & suggestions:

-       How many days are needed for a maximum tanning effect?

-       Do 1,3 or 5 coats of gelatin have an effect on tanning?

-       Testing 0,1,3,5 coats of gelatin with different ground coats (thick rosin oil, self-made varnish)

-       Trying fine pumice mixed with rosin oil or varnish as ground coat over gelatin

I will try to make my own amber varnish. Last time I did this I fused the amber myself, but this time bought the amber colophony from Kremer. Does anyone have experience with this product? I am planning to start with a 1:1 ratio of amber colophony in boiled linseed or walnut oil. Any recommendations for one vs the other?

Many thanks in advance!

 

 

As to maximum tanning, my box has 12 4-foot 40w blacklightblue (the term on the box) bulbs with a separate switch for each 6, and reflective lining on all internal surfaces.  It vents to the workshop where a wall fan moves  ozone fumes outdoors.  I do not normally spend time in the varnish shop while tanning is going on.  I place a dish of water on the floor of the cabinet to maintain humidity.  And I do check the warmth of the instrument by hand each day.

So, with those specs in mind, I can get a sufficient tan on an instrument in five 24-hour days, using all 12 bulbs, though I may drop to 6 if I am uncomfortable with the warmth of the instrument to the touch.

Admittedly, what constitutes sufficient tanning is completely subjective.  The type of bulb used matters. And checking the heat level by hand is very imprecise.  But I have not had problems with wood cracking and seams only open if I don't maintain humidity as indicated.

[David Burgess]

16 hours ago, Geigenbauer said:

 Because the fans are blowing the warm inside air to the outside, I installed an air filter at the bottom of the cabinet to prevent dust from being drawn into the cabinet. I am not sure how well this will work because the cabinet doors are not airtight and there will for sure be some leakage.

A way around the leakage is to turn the fans around so they pressurize the cabinet, with the air filter on the supply side. That way, filtered air will be leaking out of the cabinet, rather than dirty air being pulled in through the leaks.

Nice looking control unit. Will it maintain its settings if power is interrupted? Edit: Never mind, I looked it up and it will. The only downside I see is that the unit will only power 10 total watts of fans (@ 5 volts?), and I don't think that would provide as much air flow as I like with the fine filtration media I use.

https://www.amazon.com/AC-Infinity-CONTROLLER-Thermostat-Controller/dp/B00NG9TSG4/ref=asc_df_B00NG9TSG4/?tag=hyprod-20&linkCode=df0&hvadid=309779531175&hvpos=1o1&hvnetw=g&hvrand=13477476749196880120&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9016851&hvtargid=pla-570478013231&psc=1&tag=&ref=&adgrpid=62412137260&hvpone=&hvptwo=&hvadid=309779531175&hvpos=1o1&hvnetw=g&hvrand=13477476749196880120&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9016851&hvtargid=pla-570478013231

[Urban Luthier]

Wow what an impressive cabinet!! I wish I had the space to build and store something like this.

For those reading this thread looking for ideas of their own cabinet, i'll repeat the oft recommended grow tent. Cheap, easy to use and collapsable for those who don't have a ton of space. 

[David Burgess]

3 hours ago, Urban Luthier said:

Wow what an impressive cabinet!! I wish I had the space to build and store something like this.

For those reading this thread looking for ideas of their own cabinet, i'll repeat the oft recommended grow tent. Cheap, easy to use and collapsable for those who don't have a ton of space. 

That looks like a really viable, convenient, and inexpensive option. Whether a static charge builds up in the plastic reflective film, attracting dust, I do not know, having never tested it. If it does, it could be either advantageous, or a detriment. I guess I'd need to try it side-by-side with my grounded aluminum-walled cabinet to have any sort of clue.

[Urban Luthier]

2 minutes ago, David Burgess said:

That looks like a really viable, convenient, and inexpensive option. Whether a static charge builds up in the plastic reflictive film, attracting dust, I do not know, having never tested it. If it does, it could be either advantageous, or a detriment.

Humm good point David, never actually thought about that. I can say I used one of these on my last instrument and I had no issues at all with dust. In fact this is the only instrument I've mad where i didn't have to polish the top coat to get rid of dust zits. 

Next time I set it up i'll test for static and report back

[Michael.N.]

I have two 40W bulbs in my cabinet but usually I only use one. I was surprised at how effective just one bulb was, both at tanning and drying oil varnish.. I can't say I had much luck increasing RH with just a tray of water in the base. I had to go to a baby bottle warmer gently steaming away. That was after I suffered distorted plates (both bulbs on and no attempt at increasing RH). 

[Geigenbauer]

Here are some temperature and relative humidity measurements. I currently run the UV lamps for 5 1/2h with 30min off-periods in-between for a total of 22h/day. I have marked the on/off timepoints with arrows. The lamps started at 3:30pm and were turned off at 9:00pm. The temperature maxed out at about 77 deg and the humidity dropped from 41.5% down to 36.6%.

Apologies for the rough Excel job...