Post by thread:[EE] Electronics in clear resin

runawaybrainz.blogspot.co.uk/2012/04/audio-crystal-cmoy-freeform-headphone.html This is simply beautiful. I'm inspired to make something and cover it with resin. Probably a nice bright LED clock or something visual like that. Should look really nice

> http://runawaybrainz.blogspot.co.uk/2012/04/audio-crystal-cmoy-freeform-headphone.html Good job. He was lucky with the curing temperature. Not because of destroying components but because the expansion can cause 'silvering' where the resin lifts off. I'd perhaps have gone for 0.5% catalyst (which also gives the bubbles more time to escape) > This is simply beautiful. I'm inspired to make something and cover it > with resin. Probably a nice bright LED clock or something visual like > that. Should look really nice. I once made the mistake of encapsulating using a round margarine tub as the mold. Which was made from polystyrene. Fortunately the resin gelled before the tub completely dissolved, but it took a lot of elbow grease and Brasso / Silvo to get the finish I should've got in the first place I've got almost a kilo of silicone mold rubber to use up before it goes past its expiry date. The link is an inspiration, thanks The last arty thing I made was for a friend. At the hard-gelled stage of a block of clear resin he shot it with a nail gun, which shattered it internally but left the surface relatively intact. He has a small red laser pointer under it, looks good in a corner, throwing shards of light as it does, but I think a couple of RGB LEDs might be better

On Mon, Apr 16, 2012 at 7:14 PM, IVP <spam_OUTjoecolquittTakeThisOuTclear.net.nz> wrote: > I once made the mistake of encapsulating using a round margarine tub > as the mold. Which was made from polystyrene. Fortunately the resin > gelled before the tub completely dissolved, but it took a lot of elbow > grease and Brasso / Silvo to get the finish I should've got in the first > place > What material should the mold be made of? > I've got almost a kilo of silicone mold rubber to use up before it goes > past its expiry date. The link is an inspiration, thanks > What is the silicone mold rubber used for and how does one use it? Also, do you know what resin he is using? Or something similar available in Canada

One of your propane nail guns

> One of your propane nail guns? It was a butane-powered Paslode. Actually hired to figure out how they kept it firing well at low-temperature, which was a requirement for another butane project http://www.paslode.co.nz/B30090.cf

> What material should the mold be made of? Definitely not polystyrene because there's a lot of free styrene monomer, which is quite an aggressive solvent that will attack polystyrene and other plastics before it polymerises Laminating film is good, just about nothing sticks to it. Glass is OK too but you have to watch the catalyst level. More catalyst, say over 1%, causes the resin to heat up noticeably as it cures. When it cools and contracts it naturally pulls away from the glass Which should be well-polished with wax or mold release BTW If you use a lower catalyst level, for example with big pourings with a low surface to volume area ratio you don't want to overheat (they'll crack. In the lab we'd even have them catch fire if too much promoter was in the resin), the downside is that the surface doesn't move so much. What can happen then is that a part of the surface may be left stuck to the glass, whilst the rest has shrunk away from it, and leave a proud section like a thin scab For my coasters I use spun stainless steel molds. All metals are OK but the gloss you see on it is what you get, eg aluminium is easy to work with but will always produce a dull finish Most woods work but some have oils in that really interfere with the cure. I can't use some NZ native woods without precoating them with nitrocellulose laquer > What is the silicone mold rubber used for and how does one use it? Silicone mold rubber can be used to take castings of eg odd shapes. Once cured it's very unreactive (it won't even stick to itself so you can't modify a mold by adding bits). It's tough too and won't tear on undercuts etc. For example you can turn the mold inside out to remove the casting. Silicone rubber also lasts a long time and many many castings can be made with one mold On occassion I've used plasticine/plaster with a smear of vaseline for a quick casting Air (oxygen) is a ploymerisation inhibitor. So if you were casting in an open box, a piece of laminating film or metal to cover the exposed surface will ensure it cures hard. If you don't, the exposed surface will stay tacky for quite some time after the body has cured > Also, do you know what resin he is using? Or something similar > available in Canada? Any company which sells fibreglassing resin will sell water-clear as gel coat for example, or specifically for casting eg http://www.fiberlay.ca/Fiberlay_Casting_MoldMaking.pdf Fun for all the family. If they don't mind the smell that is. You would not be poular doing this in the kitchen. I have my own shed/workshop to do things like this in. And make sure you buy some acetone and rags too. It's the best and cheapest way to clean up There are a lot of fillers and glycol-based pigments too. I collect and use the very fine MDF dust from my belt sander for instance. The cast can be painted and shaped quite easily but overall is very much harder than MD

Vapor pressure of butane @ -15C leads one to suspect it's not at -15C..

1, Don't try this at hone 2. Don't smoke while you are not trying it. > Vapor pressure of butane @ -15C leads one to suspect it's > not at -15C... Tip LPG barbeque gas tank on side with valve slightly downhill. Open valve fully so gas roars out. After a few seconds starts to spit then produces more liquid then much liquid as temperature drops. Soon there is a rivulet of liquid propane/butane mix running down the bank. Unusual. Russel

Liquid feed is what I was guessing. Maybe not, though. A uC could sort out solenoid-on time ("fuel injection", it says) wih a temp sensor & lookup table. I'd be interested in a solenoid valve that small..

On Mon, Apr 16, 2012 at 11:21 PM, V G <.....x.solarwind.xKILLspam@spam@gmail.com> wrote: > > http://runawaybrainz.blogspot.co.uk/2012/04/audio-crystal-cmoy-freeform-headphone.html > > This is simply beautiful. I'm inspired to make something and cover it with > resin. Probably a nice bright LED clock or something visual like that. > Should look really nice. >

On Apr 16, 2012, at 7:01 PM, IVP wrote: >> What material should the mold be made of? > [long list of rather exotic mold materials.] The usual molds that I've seen in "craft-class" kits are polyethylene, which is pretty solvent-immune. (These were relatively old kits; I think nowadays silicone is more common. You can get some interesting shapes sold as ice-cube trays…) BillW