View Full Version : Calcium BiCarbonate
01-19-2009, 08:24 PM
I just wrapped 100 castings.
What keeps the paper so adhered to the casting when the casting is clean of anything sticky.
As I wrap, I watch the patch soak up the water and change in colour as all the white calcium bicarbonate is soaking up the water.
Calcium BiCarbonate is abrasive to an extent. The mohs is not real high vs corundum used in lapping compound.
My thoughts on this whole thing, is the calcium bicarbonate bonds to itself in the wrap. In other words, as it dries, it becomes a larger congregate.
What amazes me is the amount of sizing I can do with a patch without it degrading. My patches are .317-.318 and I size them to .309. The .314 I can see as it is only a few thousandths, but going from .318 to .309, that is a jump.
The paper after sizing is not that easy to unravel. I had a few that I tried to unravel after sizing. It was not a case of pulling an edge. The case had to be worked up to be pulled. Once it started it was simple, but, it has resistance.
Does the calcium bicarbonate actually blend in the individual layers?
Perhaps I think too much. My wife tells me I have too much free time.
I am the prime jeweler for our business, I do the design work at night after we close the shop. Today, I jacked the house to relevel it. Cooked dinner, made the bed, did laundry, cut and wrapped 100 paper patched castings, two calibers. .308, and .303 British. Oh yeah, I also redid the plumbing from the kitchen sink to the outflow pipe, with adding a vent.
I can wrap a few without feeling guilty.
It is my recreation.
01-20-2009, 05:10 AM
Doc, I believe it is the shrink that holds the paper on. Try wrapping a bullet with just one wrap. It will peal right off.
01-20-2009, 06:32 AM
Dennis, I am not sure it is shrink.
Shrink, if it is active, even the outer layer would begin to peel back on multiple layers. In effect the outer layer would shrink outwards.
It takes a couple of days for my wraps to shrink and dry so I can size. When they are dry, as you have experienced, they are hard. Sizing will cause movement between the layers.
I am wondering if there is not a chemical bonding also with the wrapping.
When the wrap is soaked, the composition of the paper changes slightly.
Calcium BiCarbonate dissolves in water. It is used in paper making, and is the main material in the making of scale in our water, and stalagtites and stalagmites in limestone caves, etc. It is also the main material in sea shells. Since it will partially dissolve in the paper, theoritically, it will rebond on drying. With the tightness of the wraps, and proximity to each other during drying, the rebonding of the calcium bicarbonate could span the layers.
It is not a permanent bond, or a strong one. It is also, mildly abrasive. Low on the mohs scale, roughly twice that of lead.
The fibers keep the paper intact while wet, and I believe the bicarbonate creates a bridge spanning the distance between the layers.
Mostly mental masturbation on my part. All I know is it works, and works well for me.
I also get bored easily.
01-20-2009, 07:33 AM
Perhaps you should examine the chemistry of the water your using.
01-20-2009, 07:48 AM
It is not the water, it is the Calcium BiCarbonate used in paper manufacture.
My main wonder in it all is the patch staying stable through sizing. I would have thought it would have been sized down, then slowly spring back opening up.
Looking into paper chemistry, my thought would be the Calcium BiCarbonate plus other aditives in the paper adhere to themselves and when dry form a bridge retaining the size.
We have more iron in the water here than scale. Our pipes are always brown inside. Our softener does pretty well with scale.
I am just fascinated with the paper staying together during the process.
I had originally thought paper patches were somewhat fragile. Not so. The twist gets quite solid. The wrap after sizing is not loose at all. It takes quite a sizing also.
It is fascinating.
01-20-2009, 10:16 AM
Today, I jacked the house to relevel it.
I bet that made your patches roll on straighter...
01-20-2009, 06:40 PM
As the paper dries, it increases in strength, as the fiber-fiber bonding improves. As water comes out of the sheet (in the three above processes/mechanisms), hydrogen bonding improves, so the fiber's bond to each other increases (as water is removed). Fibers also have "little fibers" on them, called "fibrils." Fibrils impart more contact area for more bonding. Refining (mechanical action to "brush up" the fibers tend to increase various strength properties to a point (with added mechanical energy), then it decreases if you add too much energy (and strength potential is lost).
After the fiber is dried, the fibrils are very stiff. If you recycle the dried fiber, it will be weaker the second time around, as the recycled fiber has less fibrils-they break off. Fibrils are stiff, Ever try to bend a potato chip? The "set up" of these fibrils after initial drying is called "hornification."
So, adding sodium bicarbonate (baking soda) to water will increase the pH of the water (make it more alkaline, or basic, or caustic-same thing. The pH will be greater than 7.0). The sodium bicarbonate should be dissolved fully. When you add the previously dried paper to the alkaline water (with sodium bicarbonate), you will permit the hornified sheet's fibrils to relax gently, and recover their use.
You will facilitate reversing hydrogen bonding as you are adding more hydroxl ions (-OH) to the paper in an alkaline condition (chemistry reminder. Water is HOH. When something is more acidic, pH<7, there are more H+ ions than -OH ions. When something is more alkaline, pH >7, there are more -OH ions than H+ ions). So, with sodium bicarb's addition, creating an alkaline environment, there are more -OH ions available in the water, and the hydrogen bonds can reverse an weaken bonds, which uncoils, relaxs and does not break the dried delicate fibrils. This makes the fibrils more available for the next (or recycled) round of drying after bullet wrapping.
This (alkaline pH) also causes the fibers to swell, and become more flexible. Flexible fibers are able to be manipulated (rolled, in paper patching process), without weakening. They then form nice contact with other softened, swollen fibers with high levels of intact fibrils. As the patch air dries, strength redevelops (hydrogen bonding increases). This result in a nice patched bullet. If your patch paper source is highly sized ("sizing" in paper making terms meaning the paper has chemical water resistance for sharp ink hold out and printing properites. Refer to "paper 101" thread for more info), the alkaline environment from sodium bicarbonate (baking soda) will speed up the wetting-out of the patch. If you use warm-hot water, you can speed up the process even more, as heat increases chemical reactions
When water is removed again from the wrapped paper patch, the fibers will once again form fiber:fiber bond strength as more water is removed (air dried) from the paper, forming hydrogen bonding. The drying/dewatering process makes the paper stronger as it dries (hydrogen bonds are formed as water leaves the fibers/fibrils). Since less delicate fibrils were destroyed (or more than normal levels were permitted to "play again" due to the softening action of the increased pH, offsetting the hornification of the fiber and fibrils), your resultant product will have some more stretch, and final strength benefits from having more fibrils intact in the second go around of drying (your air dried paper patch).
Calcium carbonate does not dissolve in water. If it did, it wouldn't be used as an inorganic filler in papermaking in the first place. Baking soda (sodium bicarbonate) DOES dissolve in water. It will dissolve faster in warmer water.
Paper (printing and writing grades) usually has two types of starch added to it. Internal (normally cationic or + charged) to enhance fiber:fiber bonding. It is typically added at a dosage rate of 12-25 lbs/ton of paper. There is also surface starch added to the paper. It is short moleculare weight, and is added at dosages of ~ 40-140+ lbs/ton. Surface starch is normally close to non-ionic (ethylated surface starch has a very slight anionic or - charge). When paper is rewetting, this starch (internal or surface) can provice additional bonding affect as it re-dries.
The combination of rewetting the existing internal/surface starch and the swelling of fibers/fibrils (with baking soda) will enhance sheet-sheet (or layer to layer) bonding as it redries.
01-20-2009, 06:53 PM
If I read this correctly, catboat is saying sodium bicarbonate is a good thing to soak patches in before wrapping them.
Whereas docone31 is saying the calcium bicarbonate used in paper manufacture is something that surprises him in the effect it has on paper that he soaks in (plain) water.
Is anybody else a little confused?
01-20-2009, 06:58 PM
Calcium carbonate is an inorganic filler used in papermaking. It is used in alkaline processes of papermaking (pH >7). It does not typically dissolve. It will gas off if put in an acidic environment. Antacid tablets ("Tums") are calcium carbonate. Take a Tums, and drop a few drops of vinegar (acetic acid) on it. It will bubble. The chemical reaction is allowing carbon dioxide (CO2) to gas off: Calcium Carbonate is CaCO3
It gases off in the equation: CaCO3=> CaO+CO2
CaO is Calcium oxide. It's an inert form/byproduct without much use in papermaking.
Sodium bicarbonate is "baking soda." It is not used as a filler in papermaking (because it dissolves). It is sometimes used to increase alkalinity (levels of Ca++ ions in the water chemisty of paper making) to assist with various chemical actions, such as internal sizing.
Yes, soaking paper in warm water and dissolved sodium bicarbonate is a good thing. It will aid in having fibers swell and soften. The higher pH (alkaline pH) caused by adding sodium bicarbonate ("baking soda") will break down a sheet of paper's water sizing properties, hasten fiber swelling, minimize fibril breakage, make fibers more flexible, and allow it to "wet out" faster. This is good for manipulating paper, as is needed for paper patching.
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