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Cutting premixed Shellac

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Blog entry by pjones46 posted 03-21-2011 05:50 PM 5406 reads 6 times favorited 15 comments Add to Favorites Watch

There has been alot of conversation as to how to cut a certain lb cut shellac to sume other cut. This was taken from Fine Woodworking and I hope that the table shows up corrctly but should it not refer to link:

http://www.finewoodworking.com/Materials/MaterialsArticle.aspx?id=28833

Shellac Conversion Ratios

To convert remixed shellac to a dilute cut, add the appropriate amount of alcohol, as shown in the chart. For example, to convert a 2-lb. cut to a 1-lb. cut, add 2/3 of 1 part alcohol to a 1 part existing 2-lb.-cut shellac solution.

Parts Alcohol: Parts Existing Cut

Existing
Cut 1/4 lb. 1/2 lb. 1 lb. 1-1/2 lb. 2 lb. 3 lb.
1/2 lb. 1:1
1 lb. 3:1 7/8:1
1-1/2 lb. 4-1/2:1 1-2/3:1 1/3:1
2 lb. 5:1 2:1 2/3:1 1/4:1
3 lb. 8-3/4:1 3-3/4:1 1-1/2:1 3/4:1 1/3:1
4 lb. 11:1 5:1 2:1 1-1/4:1 3/4:1 1/4:1
5 lb. 12-3/4:1 5-3/4:1 2-3/4:1 1-1/2:1 1:1 7/8:1

(Update: Several readers have questioned the proportions in the chart. The numbers are correct, however, and here’s why: The mathematics for shellac dilution do not follow a general ratio formula because you are working with the weight of a substance in a volume. For example, say you want to take a 2-lb. cut down to a 1-lb. cut. It would seem logical that it would be a one-to-one reduction of shellac to alcohol, but it’s not. When you dissolve 2 lb. of shellac in 1 gal. of alcohol, you displace the original volume by 20 percent, thus giving you 1.2 gal. total in which 2 lb. of shellac are dissolved. So a 1-gal. volume of a 2-lb. cut shellac contains only 1.66 lb. of shellac. Three lb. in alcohol gives roughly 1.3 gal; 4 lb., 1.4 gal, and so on.)

http://www.finewoodworking.com/Materials/MaterialsArticle.aspx?id=28833

-- God is great, the Beer is good and people are Crazy. www.pauljoneswoodworks.com



15 comments so far

View dub560's profile

dub560

606 posts in 1660 days


#1 posted 03-21-2011 05:55 PM

can you show me what a part looks like cause i nver get this stuff you know. i often just pour out alcohol in shellac flakes, stain and then spray

-- Life is enjoyable especially when you borrow from people

View pjones46's profile (online now)

pjones46

241 posts in 1389 days


#2 posted 03-21-2011 06:53 PM

Part refers to a liquid measure in this case(oz, cup, pint quart, etc) after the Shellac is made. This is to reduce pre-mixed off the shelf Shellac that you would purchase at the hardware store( 2lb, 3lb, 4lb are most common). I refer you to their aticle.

Mixing your own is totally different. Pound cut refers to how many pounds (weight of dry Shellack) of dry flake is desolved in a gallon (liquid measure) of Alcohol and the above pertains to the process to modify premixed shellac either bought or made.

-- God is great, the Beer is good and people are Crazy. www.pauljoneswoodworks.com

View dub560's profile

dub560

606 posts in 1660 days


#3 posted 03-21-2011 07:23 PM

still having a tough time with it but thanks though

-- Life is enjoyable especially when you borrow from people

View Bertha's profile

Bertha

12951 posts in 1439 days


#4 posted 03-21-2011 07:29 PM

For dub, the part you’re probably missing is the orignal stock solution preparation where (for example) you dissolved 3 pounds in 1 Gallon. I’ll call this 3pound:1Gallon a “stock solution”. When you buy premixed shellac, you’re buying a stock solution already prepared. From this stock solution, you take one “part” stock solution (whether a capfull, an ounce, a cup, whatever) then you dissolve that “part” of stock solution with the desired number of denatured alcohol “parts” (whatever part you defined in the first step). Of course, you could make the same stock solution in a smaller volume. For example 1.5 pounds into 1/2 Gallon & still have the same stock concentration. For example, I do just that, use 1.5 pounds into 1/2 Gallon. From there, I’ll prepare my dilutions, most commonly a 1:2. Hope this helps.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

View dub560's profile

dub560

606 posts in 1660 days


#5 posted 03-21-2011 07:38 PM

thanks bertha but what would a 1 lbs cut of shellac flakes dissolved in 946 ml(lee valley alcohol) be?

-- Life is enjoyable especially when you borrow from people

View hObOmOnk's profile

hObOmOnk

1381 posts in 2874 days


#6 posted 03-21-2011 07:48 PM

1 lbs of shellac flakes dissolved in 946 ml of alcohol = a 4 pound cut

-- 温故知新

View Bertha's profile

Bertha

12951 posts in 1439 days


#7 posted 03-21-2011 07:51 PM

I’m no mathmatician but 1 US gallon = 3 785.41178 ml, so 946 ml divided by 3785 ml= .25 Gal. So 1 pound divided by 0.25 Gallons = a 4 pound cut. A 4 pound cut is a very useful stock solution but since it’s a tad thick, I usually go with a 3 pounder. Someone here check my math, as I’m just guessing here.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

View dub560's profile

dub560

606 posts in 1660 days


#8 posted 03-21-2011 07:53 PM

are you serious, damn

ok thanks guys ..this is going to my favourite so i can use this in the future

-- Life is enjoyable especially when you borrow from people

View pjones46's profile (online now)

pjones46

241 posts in 1389 days


#9 posted 03-21-2011 07:55 PM

946 ml is approx a Quart US.(.2499068 gal) This being said, your are putting 1 lb falkes in 1 Quart which would yeild a four lb cut.

-- God is great, the Beer is good and people are Crazy. www.pauljoneswoodworks.com

View pjones46's profile (online now)

pjones46

241 posts in 1389 days


#10 posted 03-21-2011 08:03 PM

Here is a handy little free converter for the computer.

http://joshmadison.com/convert-for-windows/

-- God is great, the Beer is good and people are Crazy. www.pauljoneswoodworks.com

View Bertha's profile

Bertha

12951 posts in 1439 days


#11 posted 03-21-2011 08:06 PM

Dub, you don’t sound like you’re happy with your 4# cut :) I can’t imagine you wanted anything heavier than a 4# cut or you’d be dealing with molasses. You have a ton of options available to you now.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

View dub560's profile

dub560

606 posts in 1660 days


#12 posted 03-21-2011 08:06 PM

thanks

no i do bertha i just didn’t think it was that heavy but now i know and i can save some money in the long run. i was steady at lee valley buying these flakes but now i know…now i know. now i know(thanks)

-- Life is enjoyable especially when you borrow from people

View ksSlim's profile

ksSlim

1011 posts in 1636 days


#13 posted 03-22-2011 06:51 AM

For us “old fuds”, 1 ounce to a cup of alcohol is a 1 lb. cut.( 28.35g/236.6ml)
To dilute an off the shelf “3 lb. cut”, borrow or buy a(an) Imperial measuring cup.
OTS shellac, 2 oz. (1/8) cup,..3oz. alcohol.. should be, if mixed in the measuring cup, 5 or so ounces.
Pretttty close to a 1 pound cup

I rarely mix more than a quart at atime.

-- Sawdust and shavings are therapeutic

View DrDirt's profile

DrDirt

2597 posts in 2489 days


#14 posted 03-22-2011 05:42 PM

The tables are usefull – I usually adjust my cut depending on the temperature of teh shop and how big an area i am dealing with. When i need to thin it means I will need more coats but that is just the way of working.

I don’t recall a time where I eyeballed a 1:1 dilution and got a 2.07pound cut and had a project burst into flames but maybe I haven’t waited long enough ;-P lol

-- "If we did all the things we are capable of doing, we would literally astonish ourselves." Edison

View Bertha's profile

Bertha

12951 posts in 1439 days


#15 posted 03-22-2011 05:45 PM

Laughing with the doc^. I tend to like shellac cut very thin. For lathe work, I seem to like it very, very thin. I really only do drawer innards with the slightly thicker stuff.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

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