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Help identifying rubbery filler

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Wondering if anyone can help me identify a suitable filler to match the black material surrounding these leds.

It has a spongy consistency … you can press your thumbnail right through it easily … far softer than normal silicon.

I cut a section out and it is really easy to tear up, it has no real strength at all.

I assume its role is to weatherproof the leds, keep them aligned and provide a consistent matt background to minimise reflection.

The panel is from a sign … over 3000 leds … and ~120 need replacing. It is behind an outer perspex screen so weatherproofing is not quite as serious.

Thanks for any help.



Liquid electrical tape?
Mmm ... never used it before. I did find a video showing it, but it sets very hard. Probably harder than normal roof and gutter silicone ... which is still 3 x harder than the stuff I'm trying to replace. Thanks dknguyen.


Thanks Bob, that looks pretty much what I'm after. The video even showed the material ... Dow Corning SE-9187L.

It's available via element14 with a 7 day wait for it to come from overseas. $92 for 330ml.

According to the specs it has a Durometer/hardness of 17A which is around the level of chewing gum ... and a bit softer than a rubber eraser ... which fits with what I've got.

Thank you very much for your help.


This may also work and be rather quicker and cheaper to obtain.

It's slightly firmer than the Dow one, 24 rather than 17 Shore A, but in stock and less than a third the price
Yes, I can see that would be worth trying for sure. Thank you.

I'm in Australia, so it could take a little longer ... I checked our Aust RS site and while it doesn't have quite the equivalent in black ... it's pretty close ... but for both the white and the black it states ...

"Stock check temporarily unavailable - call for stock availability"

Here's a place that you can get the SE-9187L for almost 1/2 the price of E14:
Thanks, I had been looking for other distributors of Dow gear in Aust and had come across Ellsworth ... but I couldn't find any prices ... and in the end started to wonder if they were only in SE Asia and not actually in Aust.

I'll see if I can find a number to call in the morning ... definitely worth it to save that amount of money ... though their website says "Usually Ships in 2-3 Business Weeks. NON-RETURNABLE."

If they say 'usually' ... you can bet it's never any quicker ... it's always going to be longer!!! ...and I can't afford too much more delay.

Took me a week to get in all the samples of leds to find a match for the originals ... a day to stick them on a breadboard and get the owner in to make sure he was happy with the 'colour' ... and then another week for the 130 leds to arrive. I should have started chasing this silicone earlier.

It's pretty much at the stage where a bird in the hand is worth two in the bush!! I am pretty confident of element14's 6-7 days ... as long as I order on Monday.

Thank you both for your help.


Time for an update.

The silicone turned up on time and is a real pleasure to work with. Got to be careful with the caulking gun as it will run out of the tube ... but the self leveling is excellent ... looks really good with no effort.

It's a bit shinier than the old stuff ... whether that's because it's a different product ... or coz the other stuff has been out in the elements for 10 years. Either way ... far far easier than trying to scrape in and smooth regular silicone ... and more than a few feet away you can't tell anyway. Plus once the leds are on, you need sunglasses to avoid the glare.

Looks like any spillage is best cleaned up after it has set ... just scrape it away.

Thanks BobW for directing me to a suitable product ... and you other guys for your help as well.

Thank you.

20180523_112949_resized.jpg 20180523_120406_012_resized.jpg


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From your description it sounds like polyurethane potting compound. This is typically less expensive than other materials and it's softness is preferred to reduce tensile stresses on pots longer than a few inches.
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