CurtPalme.com Home Theater Forum

Francisco · Joined: 05 Apr 2007 Posts: 305 Location: The Netherlands

So Curt what do you advise me to use ethylene or propylene glycol? (if prize is not the issue)

jbmeyer13 · Joined: 03 Dec 2010 Posts: 1135

Francisco · Joined: 05 Apr 2007 Posts: 305 Location: The Netherlands

Well it's not so easy, found out that Propylene glycol has a different breaking index than Ethylene glycol, and it is not reccomended for LC coupling. For a AC unit it's useable.
Does someone knows what Barco uses in their mixtures?

70-30%
or
80-20%

Hulio · Joined: 15 Apr 2006 Posts: 469 Location: Belgium

It seems that the ideal cocktail is 80% ethylene glycol and 20% glycerol. In this article is explained why :

" To date, ethylene glycol, mixtures of ethylene glycol and glycerol, and mixtures of ethylene glycol and water have been employeer extensively as coupling fluids in projection TVs. The preferred fluid in recent years has been ethylene glycol/glycerol mixtures due to the relatively low volatility of the constituent components. As a result, the loss of coupling fluid through the last lens element of the projection lens system has been minimized. Also, the refractive index of an ethylene glycol/glycerol mixture is higher than pure ethylene glycol or a mixture of ethylene glycol and water. In addition, ethylene glycol/glycerol mixtures exhibit reasonable environmental friendliness, the ability to operate near 90° C., low cost, good compatibility with molded optics, good thermal conductivity, and good optical clarity.

A preferred composition for coupling fluids of this type has been 80% ethylene glycol and 20% glycerol. Further addition of glycerol would cause the projected image to squirm, due to natural convection associated with thermal gradients in a viscous fluid.

Mixtures of ethylene glycol/glycerol, however, do have some properties which limit their usefulness. For example, the inherent electrical conductivity of this mixture is a problem. If an accidental spill occurs and the fluid gets onto a printed circuit board, the board has to be discarded to avoid electrical malfunction and even possible fire caused by the relatively high electrical conductivity of the fluid. Even more basically from an optics point of view, the refractive index of the mixture is lower than desired. Accordingly, couplers employing this mixture still suffer from relatively high levels of reflection at the CRT/coupler fluid interface. These reflections, in turn, lower the overall contrast of the projected image, making projection televisions less acceptable to some users in comparison to direct view televisions. "

GREG1292 · Joined: 10 Oct 2006 Posts: 417 Location: indiana

Need a link going to replace the glycol in my 9500 how much do I need and where
do I buy it? Need enough for 3 tubes.

tschaeikaei · Joined: 08 Apr 2013 Posts: 489 Location: Germany/Saarland

You'll need about 550 to 600ml per tube, so be safe and buy 2l. Please don't ask me about gallons, sounds like a sail ship to me.
I do use MONOetylene glycol pure, some others do as well and i don't know about problems.
If i had to replace my projectors coolant today, i'd definitely try this stuff.
http://www.curtpalme.com/forum/viewtopic.php?t=37673
If it is optically at least as good as glycerine/glycol, it will not corrode the aluminum. And that's something desirable.

Be sure to repaint your housings after cleaning out all the old stuff.

Regards, Julian

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I'm redoing my 9500LC's CRT assemblies today. I just got done draining all three assemblies and got almost exactly 64 ounces out of the three.

Allowing for a little spillage and some that got cleaned up with a rag, that didn't make it into the measuring container, let's say 66 ounces, 22 ounces per assembly. This should give you a full fill and maybe an extra squirt.

I recommend that you coat all screw threads with light grease or heavy oil before reassembly, even if you use stainless hardware,
because it can't do any harm to do so.

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

For those few who are still interested in this, I bought food grade glycerin and glycol both from a couple of ebay sellers.

2 gallons of glycol for about 35 dollars a gallon, a quart of glycerin for about 15 dollars.

I'm going to mix a batch at a 20 percent ratio. I'll be watching for that squirming effect, which should NOT occur if the glycerin
content is low enough. I've experimented with small quantities and it certainly appears that the lower the glycerin content, the less the mixture wants to squirm when stirred.

greg9518lc · Joined: 19 Apr 2016 Posts: 360

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I started with a small quantity of pure glycerin (5 CCs) and added glycol and mixed it thoroughly, 5 CCs at a time, to achieve mix ratios of 1:1, 2:1, 3:1, 4:1, 5:1, etc. up to 9:1. (10 percent)

When I reached 4:1 (20 percent glycerin) then all visible squirming stopped. At any heavier (glycerin) concentration,
squirming could be observed when looking through the mix while stirring it even if it had been very thoroughly stirred for quite a while already.

So I believe that a 4:1 mix, 20 percent glycerin formula is a very good place to start.

When I mixed up a gallon batch, I did it a quart at a time and my findings in the quart mixing cup
matched up perfectly with my small scale test. When glycerin is not more than 20 percent by volume,
then all visible mixture squirming goes away.

I have a refractometer but it doesn't go high enough to measure the index of refraction for glycerin/glycol. It's off the scale.

I should buy a wider range refractometer and make an attempt to come up with a mix that matches 3M's recommended index
of refraction in an LC system. But I need to find that document again. I had it but can't find it.

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

Actually I just found the document. It's on Chris Stephen's xymox website.

Excerpt from it:

whoopn · Joined: 08 Mar 2016 Posts: 34

So I've read through everything I've been able to find on this and I have found the following statements:

One person says we can't use Propylene Glycol, we need to use Ethylene Glycol b/c LC doesn't work well with Propylene Glycol.

The previous post to this mentioned the ratio needs to be 80% ***ylene Glycol and 20% Glycerin.

So we have two truth statements I'm seeing:
1. Use Ethylene Glycol
2. Use 80% Ethylene Glycol with 20% Glycerin

Am I missing anything?

So how truthful is the ethylene vs propylene statement?

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

The correct answer with regard to the mix ratio for ethylene glycol and glycerin:

Whatever mix ratio which achieves a match between the index of refraction of the glycol mix and the index of refraction of the CRT face glass is the proper ratio.

That is somewhere in the general vicinity of 1.5 (green color) if I remember correctly.

Propylene glycol MAY be usable if it is (A) water clear and has no tint, (B), is non-corrosive/non-acidic and unlikely to cause chemical degradation in the optical cell assembly, and (C) has a compatible range of index of refraction.

As a general rule of thumb, you can see for yourself if the index of refraction is "good enough" by filling a coolant cell assembly with the coolant to be tested and then illuminate it and the CRT face with a bright light. Ideally you will never actually see the face of the CRT, but you will see only the phosphor layer. If the surface of the CRT face itself can be seen, either as the CRT face or as a reflection, then the index of refraction is too far off to be a good match.

whoopn · Joined: 08 Mar 2016 Posts: 34

Ok, any idea what barco's fluid used to be?

I can't seem to buy any of this stuff anywhere already mixed so I'm forced to make it myself and as I am not a chemist nor an optics engineer I'd like to have a standard to know what someone else uses and if it was successful.

I have a barco 1209, id love to just buy the right fluid straight from them but they don't LC anymore and they haven't made a CRT in a while.

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I work for a company that has been refurbishing crt assemblies for flight simulators for many years. We use straight EG and it works to the complete satusfaction of all our customers so just use that and don't sweat over the details.

whoopn · Joined: 08 Mar 2016 Posts: 34

Ok, I'll do that, what had me guessing the most was what "squirming" is, is there an example somewhere of what to look for?

I typically don't care about video issues unless I notice them, then I can't stop caring about them. If I went straight EG then I could add glycerin like you did in your grand experiment to determine your 80/20 ratio, but that was with a marquee right?

whoopn · Joined: 08 Mar 2016 Posts: 34

Also, where do you buy your Ethylene Glycol? I'm not having a lot of luck.

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

ebay!!!

Squirming is a visual distortion that occurs if the glycol/glycerin mix is not completely mixed. It resembles the heat wave distortion you see just above the roof of a black car on a hot sunny day.

It is possible for well mixed glycol/glycerin to start separating, aka "stratification" and when this happens you may see squirming in the image. It should go away by itself from convection currents in the glycol as the tube heats up in operation.

whoopn · Joined: 08 Mar 2016 Posts: 34

Ok thank you for your excellent help