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From: Don Y <blockedofcourse@foo.invalid>
Newsgroups: sci.electronics.design
Subject: Re: poor man's decal
Date: Thu, 3 Apr 2025 12:42:48 -0700
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On 4/3/2025 1:11 AM, Liz Tuddenham wrote:
>>> There is an adhesive called "Copydex" in the U.K., which is a latex
>>> emulsion that becomes rubbery when the water component evaporates.  "Low
>>> tack" would be a polite way of describing it - the problem isan't
>>> removing it, but getting it to stay on in the first place.  I have used
>>> it to stick paper copies of the artwork onto the  front panel to use as
>>> a drilling jig, then it can be peeled off easily.  The latex tended to
>>> wrap itself around the drill bit  . . . followed by the paper label.
>>
>> Yes, we have similar adhesives ("rubber cement", etc.).
> 
> There are some very strong rubber cements with organic solvents, Copydex
> is a water-based emulsion and is very weak.

"Rubber cement" (generic) is generally regarded as a poor adhesive,
here.  It is often used just to glue paper objects together (e.g.,
photos, collage, etc.).  The fact that it can be easily removed
(e.g., for mis-application) is an asset.

It is not generally regarded as a good long term adhesive because
it tends to "rot" (for want of a better word).  It is also often
acidic so can damage the items adhered with it.

Perhaps the most notable part is that it can be used as a sort of contact
adhesive (apply to both surfaces, let dry, mate) instead of having to
work with it "wet" (which is also possible but a bit messier)

>> But, some applications deliberately want low tack (e.g., in masking
>> artwork)
> 
> That's the sort of thing Copydex is used for, you can rub it off with
> finger pressure.

Ditto with the rubber cement.  You don't end up with the "super-glue"
situation (where your finger now wants to stick to everything!)

>> I used a spray adhesive to repair a headliner.  Granted, it's not
>> a heavy weight to support.  *But*, it is "upside down" perpetually
>> (so, gravity is trying to pull it off) and very large (a dozen square
>> feet?).
> 
> The area shouldn't matter, for every extra square foot of material there
> is an extra square foot of adhesive.

But applying and removing it present challenges.  Imagine one of
your project boxes that is 4 ft by 4 ft and trying to get things
aligned -- while working on it FROM BELOW!

>> (I have nothing
>> stronger than xylene and MEK on hand
> 
> Either of those should work.

I would hope NOT to need to resort to either of those.  I always prefer
using the least volatile/active substance that will meet the challenge
out of respect for the other parts involved (e.g., acetone makes a mess
of most things).

Remember, there are other things beside the panel that can come in
contact with any applied solvent.

>>> After fixing the acetate sheet I burn them through with a soldering
>>> iron, then trim up the flash with a rat-tailed file (file towards the
>>> panel, never away from it).  On that particular piece of equipment, I
>>> may have cut around the meter hole with a knife because it is rather
>>> large.
>>
>> A *pointed* Xacto knife isn't suitable for the whole task?  Or, do you risk
>> the cut "tearing"/"running" through the acetate to areas undesired?
> 
> The holes produced that way tend to be jagged and the knife is soon
> blunted by cutting into the aluminium panel.

OK.  Even a swivel blade would "find" the panel.

> A soldering iron gives a
> nice smooth finish but throws up a 'flash' of melted material which is
> easily trimmed off with a file.  It is a quicker and more accurate
> process than trying to cut tiny circles with a knife.  The knife is good
> for trimming excess tape off the outside edges.

What about a rotary tool like a dremel to abrade the plastic that
isn't "backed" by aluminum?

I am planning on just using punches to knock out any holes (in the
laminate and/or printed sheet) BEFORE mating to the panel.  Any
holes (though the entire decal) would also serve to orient the
decal to the panel; less chance of it coming into adhering contact
in the wrong place...