Methylcellulose CPS

[himanshu]

Hi!

I would like to start using methylcellulose for my Origami projects. The supplier, where I enquired for the chemical, wants me to specify the CPS.

Can someone tell me what is CPS? I really have no idea what it means.

Thanks.

Himanshu.

[wolf]

CPS is short for centipose, a measure of the viscosity of the chemical (when mixed and tested according to some criteria). The higher the number, the more gooey it is.

For folding, you'll want something between 2000 and 4000 cps.

[Joseph Wu]

Of course, it would be much easier to tell them you want it in powder (dry) form. That way you can mix it up yourself and not worry about the CPS numbers.

[wolf]

Well...not quite. Methylcellulose in dry form will also have a CPS specification. The cellulose part of MC is a polymer, so it's possible to have different numbers of functional groups, substitutions, and so on. Different polymer chain lengths will result in methylcellulose with slightly different properties, such as viscosity.

If you get MC with very short polymer lengths, it may not reach the viscosity you need, no matter how much of it you use for a given amount of water. So generally you'll want to go a bit higher, if you want to whip up a batch of goop for folding.

[Joseph Wu]

Good point. Can you tell I've not had anything to do with organic chemistry for the last 17 years?

[himanshu]

Thank you for your replies Wolf and Joseph Wu!

Another query:

In my country, nobody manufactures methylcellulose. It is normally available as an imported pack of 25 kgs. But my supplier has agreed to break open a pack and give me a smaller quantity.

Now, I would like to know, what quantity should I buy. Or, if you can tell me how much of the 3000 cps chemical is used to treat a 60 gsm handmade paper for sizing, I can calculate my requirement.

Btw, is the standard MC to water dilution rate 1:10 or 1:4?

[wolf]

Now that's going to be a tough one to estimate. It depends on how much sizing the paper already contains, and what you're trying to do with the paper. There isn't a standard dilution rate either; again, it depends on what you want to do. You're going to have to experiment to find out what works for the kind of paper you're using.

I'd say go for the 25kg bag, then you never have to worry about MC ever again.

[esato]

As we are talking about MC, I would like to ask you (wolf!) some questions.

Wolf wrote in another topic a way of applying MC to the paper, which basically consists in lying the sheet of paper on an acrylic board and using a brush to soak the sheet of paper with a solution of MC.

If I want to strenghen tissue paper, so that I can fold insects or anything which requires extremely thin paper and it won´t rip, what viscosity should the solution have? Sould it be like the white of an egg?

Secondly, I have tried the above method but only in about one out of five times the result is ok. When the paper gets wet, its size grows and wrinkles and bubbles appear. If I remove the wrinkles and bubbles, when the paper dries it shrinks and some parts get ripped. If I don´t remove the wrinkles and bubbles the sheet usually won´t rip, but instead it will end up not being crisp and smooth, its surface gets irregular.

What am I doing wrong?

[polop]

rippleing is worse in some papers than others. also It can be cured. Half way through the process of drying lift the paper off the plastic and place it carefully back onto the plastic making sure that the paper is no longer rippled do this at regular intervels. If you are using lesser grades of paper this technique will be more difficult as the paper wont be strong enough to be supported when wet. I recomend mulbry paper it is thin and strong when wet. as for buying mc I use wallpaper paste. It comes in a wight powder is easy to mix and also is very cheep(it also contains insect repelant ). As for 25kg of mc, that will last you for years of constant folding, It only takes 1 teaspoon in a 1;9 concentration for a 20cm sheet!

[wolf]

In this case it sounds like it's not the viscosity that's the problem, but rather how you apply it.

If you put the dry sheet on the acrylic board, and then drop a lump of goop in the centre before brushing it out, chances are that the paper will start expanding unevenly.

Instead, the method I use is this: first, stick one edge of the paper down onto the board with MC (a single brush stroke along the edge will do). Let's say we work our way vertically downwards. So, the first brush stroke will be applied horizontally at the top edge of the paper. Then, apply goop horizontally below this, working your way out from the central axis of the paper. Everytime you work on one strip, make sure that you pull slightly on the lower (dry) edge of the paper.

One thing to keep in mind - for any particular part of the paper, brush only in one direction. Reversing brush strokes while applying the goop will cause the paper to pucker up and wrinkle.

Here's how the brushing would look like in a crude representation:

Code: Select all

arrows indicate brushing direction:
---------------------------
|        <--|-->          |    <- goop here first
|        <--|-->          |
|        <--|-->          |
|        <--|-->          |                |
|        <--|-->          |                |
|        <--|-->          |     work this way down 
|        <--|-->          |                |
|        <--|-->          |               |/
|        <--|-->          |
---------------------------   <- always maintain slight downward tension here