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I heard the term "re-enterable potting compound", which is a gel-like (possibly hard?) material that can be used to fill electronics enclosures for water intrusion protection and other things.

What is meant by "re-enterable", exactly, and what forms does it tend to come in?

I assume this means that it can be removed and the device re-worked if necessary, although it could simply mean "probe through".

If my assumption is right, how does one "re-enter"? How is the compound cleaned without damaging any electronics or other possibly sensitive items that it's covering?

I used to work with PCBs and transformers that I suppose use non-re-enterable potting or conformal coating, and re-working those can be a huge pain, but probing was never a problem (on the PCBs). A sharp thin probe would work, and the hole could be repaired.

Here is another question about removable water protection, however "re-enterable" isn't used anywhere. I presume the answer there by D_Weight might be close.

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    \$\begingroup\$ According to youtube it means you can poke through it with a probe. 3m Scotchcast gives you a gel that you can poke a probe through and will subsequently reseal. Their product video shows a weatherproof poolside line voltage electrical junction box sealed with it. Altogether not a horrible idea, but probably excessive in a weatherproof residential box, but they bypass the complications of pouring an electrical box already mounted and run in conduit. Often when terminology or lack of documentation is an issue you should pop by youtube as there is plenty of corporate promotional video. \$\endgroup\$
    – K H
    Commented Jan 5, 2019 at 3:16
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    \$\begingroup\$ There is a rule of thought that says the easier it is to poke , the easier it is for vapor pressure to creep thru. This is why Sumuto's black epoxy has the higher moisture rating and clear epoxy for LED's requires baking if unbagged and exposed to humidity after a few weeks to avoid popcorn stress in solder reflow. Potting compounds come in various silicone and polyurethane mixes with various density and moisture absorption rates. So it depends on your criteria. For automotive it's hard thermal or UV cured silicone polyurethane, as I recall. \$\endgroup\$
    – Tony Stewart EE75
    Commented Jan 5, 2019 at 3:26

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I've used raytech magic gel which is one of the more commonly used re-enterable potting compounds.

The mixed compound starts off with a consistency like that of a weak sugar syrup, after a while it sets into a fairly tough greasy (with silicone) jelly. you can bounce things off it and it's fairly resistant to being torn.

To get it off you tear or cut through the gel to get the board or wires out, and then clean the remainder off. I used Iso-propanol and compressed air which did the trick fine.

The videos on their site show what the stuff is like to work with. I'd recommend it - at the cost of silicone all over my lab and hands, it's saved me having to rebuild things from scratch.

The other reason to use it is the chemicals are much better for aquatic life than the typical bis-phenol-a based potting compounds.

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  • \$\begingroup\$ Thanks for the response. I'm hoping for more comprehensive information, but this is useful. \$\endgroup\$
    – Steve
    Commented Jan 11, 2019 at 1:26

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