Hot glue for a mold - Success!

Blaxmyth

Blaxmyth

Sr Member
Trying to find a cheap way to make quite a few low relief castings in resin, stiffened with fibreglass.

Can't afford any Silicon RTV - although it'd be lovely - and I've heard that hot glue can be used as a mold. Sounds appealing because it's cheap and flexible.

Has anyone had experience with this - good or bad?

Regards, Phil
 
Last edited:
Re: Anyone used hot glue as a mold?

Haven't personally tried it yet, but another cheap option I've seen mentioned online a few times and in a theatre prop making book is 100% silicone caulk from home improvement stores. No where near the cost of RTV silicone, but good enough for limited castings, and sounds like a good option for your circumstances.

This was also posted to (I believe?...) the open RPF Facebook group not too long ago:
Economical Silicone Molding tutorial - YouTube

As for hot glue, that's even cheaper than the caulk, but unfortunately I haven't personally tried it or seen it recommended very frequently, I've only seen it used ONCE as a cheap casting material, but not the mold.

Hope that helps, good luck.
 
Re: Anyone used hot glue as a mold?

It certainly is useful. Thanks for taking the time and trouble to check this out!
 
Re: Anyone used hot glue as a mold?

I use hot glue if i dont have any rubber/silicone to make a mold. Depending on the part i use talc or PVA (polyvinyl alcohol) as release agent.
Sometimes i even used silicone spray from the garage as mold release if the surface is less important :p

I usually to this
Put the part on a flat surface, like a styrene sheet
Box it with walls around it, ½ inch above the highets point
Spray it with PVA alcohol, rubbing it with carnuba or using talc (or silicone spray)
Adding hot glue to get one layer, let it cool and then put on some more to get it rigid. About 5mm thick (0.2 inch)
Then i add plaster with microballons in it, to get a sturdy mold

If i use this method, its a quick part i need and nothing im gonna use alot. It has a short life and will wear out quickly.
When i want something to last 2-3-4-5 runs, i usually use latex closest to the part, hot glue on the outside, and then plaster to get a sturdy form.

There is probably 10 ways to do it, i dont know wich is the correct one, but this works for me :)
(Test the hot glue you use before making a big mold, different brands have different success rates i noticed)
 
Re: Anyone used hot glue as a mold?

Wow! This is great advice - thanks indeed!

I just made a small test in the shed - very cold out tonight - and I found that ordinary car wax smeared over a bondo master worked well. The hot glue set quickly and popped off without any problems, and appears to have accepted sufficuent detail for the project I have in mind.

Thanks for your help, DOOM99 and HCP. :thumbsup
 
Re: Anyone used hot glue as a mold?

never even thought about doing it with hot glue before.. could be very handy for small items if im in a hurry :)
 
Re: Anyone used hot glue as a mold?

Looking forward to seeing the results of this! The possibilities would be endless. Another great thing about hot glue molds, as Blaxmyth pointed out to me, they can be melted down and reused!
 
Re: Anyone used hot glue as a mold?

I've just spent an hour or so getting the master mounted on a piece of plywood. Need to place a bed of bondo around the edge of the master to allow a deeper draft than at present. Might as well take my time and do a proper job - or at least fail more definitively...
 
Re: Anyone used hot glue as a mold?

Well, got the mould finished this morning and made a successful test this evening!

Phase 1 - mount the master on a 12mm thick piece of plywood, being careful to eliminate undercuts.
DSC03975.JPG
Phase 2 - resin coat to seal the plywood and the master.
Phase 3 - liberal coating with car wax - the paste stuff, not the super expensive carnuba.
DSC03976.JPG
Phase 4 - build a dam wall to contain the hot glue.
Phase 5 - pour in hot glue - melted at a medium heat on the kitchen stove in an old cooking pot, then poured veeerrry carefully onto the master - I built up a thin spot with the hot glue gun once the glue had hardened sufficiently
DSC03977.JPGDSC03978.JPG
Phase 6 - separate the mould from the master - took a while and taught me that I needed to wax the edges of the ply underneath the aluminium strips
DSC03979.JPGDSC03982.JPGDSC03984.JPG
Phase 7 - wax the mould and pour rondo in - embed several small pieces of fibreglass cloth inside just for added strength
DSC03985.JPG
Phase 8 - cook for about an hour in a cabinet heated with an 80 watt bulb
Phase 9 - flex the mould and the cast pops out - the hot glue becomes more flexible in the curing cabinet, but still retains its strength
DSC03986.JPGDSC03987.JPGDSC03988.JPG

Success! :D
 
Can you get vinamold over there? Its a silicon type rubber that you can melt down and reuse. It holds alot of detail and you can melt it in the microwave :)

I paid around £6/kg :) So it may work out cheaper than glue sticks for slightly bigger jobs.
 
Re: Anyone used hot glue as a mold?

D00M99 said:
Haven't personally tried it yet, but another cheap option I've seen mentioned online a few times and in a theatre prop making book is 100% silicone caulk from home improvement stores. No where near the cost of RTV silicone, but good enough for limited castings, and sounds like a good option for your circumstances.
Click to expand...


I've done this for some small props that I wanted copies of. The key, I've found, is to make the first coat very thin, but make sure to really work it in tight to get all the detail. I used wet fingers (the water prevents the silicone from sticking to your fingers) to smooth it all on. After the first coat dries, add enough coats to make a sturdy mold.

It works pretty well, the molds last longer than I expected, and the price certainly is right. :)
 
Hmm - just made a second mould with the same master - long story - a mate of mine has a project that needs a swag of these fleurs, and I'm wanting about five moulds minimum so I can pour the resin in batches.

Anyway - the glue is cooling as I type this, and I've noticed a lot of bubbles from around the edge where I had waxed the cardboard. It seems that I need to wait until all the solvent has evaporated from the wax before pouring the hot glue on top. I'm guessing the bubbles are the solvents for the car polish wax I'm using. Just something to bear in mind - let the wax cure in a heated cupboard for 24 hours before pouring glue onto it.

On a more positive note - my wife actually invited me to use the kitchen stove to heat the glue, because it's winter here in New Zealand and the shed is a little chilly. :D
 
Blaxmyth said:
On a more positive note - my wife actually invited me to use the kitchen stove to heat the glue, because it's winter here in New Zealand and the shed is a little chilly. :D
Click to expand...

Dude, dont make a mess, those offers are once in a lifetime! :D
 
This thread is more than 7 years old.

Your message may be considered spam for the following reasons:

  1. This thread hasn't been active in some time. A new post in this thread might not contribute constructively to this discussion after so long.
If you wish to reply despite these issues, check the box below before replying.
Be aware that malicious compliance may result in more severe penalties.

Similar threads

Jimmer
Help requested..confusion on a glue kit
Replies
2
Views
582
Jimmer
Jimmer
Cadger
Loose X-wing cannons - modeling noob needs glue tips
Replies
17
Views
1,216
rbeach84
rbeach84
JimmyB
Voxel Hollow: Blender addon for hollowing a mesh for 3D printing
Replies
0
Views
204
JimmyB
JimmyB
jake88
Best glue for foamboard?
Replies
3
Views
753
swgeek
swgeek
rjenkinsgb
Help creating a realistic animal (bird) "skin" for an animatronic model?
Replies
12
Views
1,199
publiusr
P
Back
Top