By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Forum House Ad Zone

Painting blue styrofoam

All Topics | Latest Posts

Search for:  in Thread Title in  
1 2 Next > Last >>
Simon Young 120/01/2012 09:24:46
4 forum posts
Hi Guys and girls,

Just joined your forum after being a lurker for a while.

I'm hoping that someone can help me with a dilemma - I am having a hell of a job getting a good finish on a panel I'm wanting to paint. Its made from standard blue styro but having cut it and sanded it to death it looks really fine to the naked eye - but when I paint it I cannot seem to get a nice smooth enamel type finish without any lumps bumbs or grazes showing.... can anyone advise whats the best paints to use so that I can dip the panel and get a really high quality paint finish without having to keep rubbing down and panting and then putting another coat on - surely there is a way to dip it and get a nice finish straight away. All help appreciated.

Simon
Ian S C20/01/2012 10:04:37
avatar
7468 forum posts
230 photos
Hi Simon, don't know how you get a good finish on foam, I had enough trouble getting a paint that did'nt disolve the foam, I found an aerosol craft paint (silver), that worked, I was'nt worried about finish, it was for the foam displacer in a low temperature stirling engine, the foam I had crumbled a bit, so the paint was to hold it together. Ian S C
Richard Parsons20/01/2012 11:40:14
avatar
645 forum posts
33 photos
Hi all
Try this tick, Mix your paint/varnish with French chalk. Make it a thick-ish mixture. Slap iy onto the surface and let it dry for a few days then sand it.
Rdgs
Dick
Gordon W20/01/2012 12:06:21
2011 forum posts
I've used houshold water based paint (in the house) to paint styrofoam and polystyrene, seems to work well, you might need several coats.
Les Jones 120/01/2012 12:27:56
2292 forum posts
159 photos
Hi Simon,
You could try a thin mix of "Polyfilla" (Or similar) painted on.
 
Les.

Edited By Les Jones 1 on 20/01/2012 12:28:48

Springbok20/01/2012 12:36:34
avatar
879 forum posts
34 photos
Simon
Firstly welcome to the forum I have found that a standard B&Q emulsion paint will act as a good base basically anything you have left over in the garage. let dry for a few days sand then put your finish on.
 
Bob
wotsit20/01/2012 14:51:46
188 forum posts
1 photos
I coat lost foam casting patterns with a thin mix of the sort of plaster used for jointing drywall (a small sack goes a long way). The mix is about the thickness of cream, and the pattern is simply dipped in it and allowed to 'drip-dry'. I wasn't trying to get a good finish - it is to prevent the casting sand collapsing into the mould at the instant the hot metal replaced the foam. Lots of people recommend latex paint, but it never covers properly, as Simon noted.

It might be possible to do this, then clean up (sand?) the plaster, and paint afterwards - for casting, I never cared about the outside finish. I assume you are using the 'hard' dense coloured foam used for building, which can be machined and sanded very smooth with care, not the white packaging type foam.
 
Another consideration might be that this stuff has horrible 'attractive' properties due to static electricity (I think) - I find I can get it apparently extremely smooth to the touch, but looked at closely in a strong light, it is covered in the dust produced by sanding it - maybe you can take it into another room and blow the dust off.

Clive Farrar20/01/2012 18:15:53
avatar
125 forum posts
41 photos
I use this stuff in model aircraft and would never dream of painting straight onto it.
 
there are so many micro cavities to fill the weight penalty is horendous.
 
I use brown parcel paper slap a coat of diluted PVA onto the paper.
Sponge a THIN coat onto the surface of the foam then bring the two together.
Leave a couple of days then paint as normal.
 
If you are doing this for a casting then you dont even need to paint it .
 
Regards Clive
John Rudd20/01/2012 20:18:54
1479 forum posts
1 photos
Simon,
 
I also fly r/c models (I've also flown with and know Clive the prev poster)...
 
So what he said.....Brown paper covering with diluted pva...us modellers use it all the time.... A fellow flier we both know as Mac, swears by it and paints his with the small sample pots obtainable from the likes of B&Q....

Edited By John Rudd on 20/01/2012 20:19:32

Stub Mandrel20/01/2012 21:31:59
avatar
4318 forum posts
291 photos
1 articles
> paints his with the small sample pots obtainable from the likes of B&Q....


They are handy, aren't they!

Neil
Terryd21/01/2012 00:18:15
avatar
1946 forum posts
179 photos
Hi Simon
 
I second Bob's recommendation. Emulsion is cheap, inert and thick enough to fill imperfections. It dries quickly and several coats can be applied. Leave to dry thoroughly and then sand to get a good finish. you can then paint with whatever finish tickles your fancy,
 
Regards
 
T
Billy Mills21/01/2012 00:39:19
377 forum posts
1829 paint from B & Q is a "Chalky" emulsion , about £2.10 for 100 mL Tester pot. Dries fast and levels very well.

Billy.
Simon Young 123/01/2012 12:29:44
4 forum posts
Thanks for all the replies guys it really is appreciated.
 
I am trying to make basically some struts that are 10mm tubes and 100mm long, I am drilling a hole right up the middle and inserting a 3mm bamboo stick for rigidity. So I am then left with what looks like a column made out of styrofoam.... I am drilling these shapes out using a high speed drill with a steel tube (shamfered end) - but the finish on the plugs created is poor... sanding them still leaves an unsatisfactory finish (I have cleaned the tube and also lubricated while drilling - still not good enough)....
 
When I cut the foam using a hot wire obviously this leaves a perfect smooth surface as its being melted at the same time as being cut.... if only I could cut the perfect 10mm column using a hot wire I would have what I want.
 
I presume there are other grades of blue styrofoam - perhaps I'm using the wrong material to start with as its to soft? Anyone with experience can help with this????
Martin W23/01/2012 15:26:57
940 forum posts
30 photos
Simon
 
Would it be possible to use a very thin wall plastic tube and then core it with styrofoam. This would give a very smooth outer surface while the styrofoam prevented the tube from collapsing. A small stick could still be added if the composite structure wasn't rigid enough.
 
Just a thought as they say.
 
Martin
 
PS
 
When I used to fly RC helicopters I used a very thin high gloss heat shrink as a finishing cover on the rotor blades and tail boom. I don't know what the shrink temperature of this was, used my good lady's hair dryer if that helps, but if it is lower than when styrofoam loses stability then it could be used as a finishing surface.

Edited By Martin W on 23/01/2012 15:36:07

Billy Mills23/01/2012 15:32:04
377 forum posts
How about foam on steel rod for support then mount in lathe between centres with hot wire as cutter, turn slowly by hand.
 
 
Billy.
Keith Long23/01/2012 16:14:29
883 forum posts
11 photos
Could you make a hot wire cutter in the shape of a loop (might need to be 2 turns rather than 1) and then use that to cut a "dowel" shape out of the foam. Drill the hole for the bamboo either before or after which ever is easiest, or just sharpen the stick and push through. You could even drill the hole with a piece of hot wire of a suitable size.
Keith
Simon Young 123/01/2012 16:31:05
4 forum posts
The problem I have with the hot wire is getting a perfect circle it seems to distort or I wobble on the way down! I have looked everywhere on the web for a styrofoam dowel but it doesnt seem to exist! If I had a tool to cut the styro dowels with hot wire then I would be away as the heat seals the surface as drilling them just gives a rubbish finish...
Keith Long23/01/2012 17:36:21
883 forum posts
11 photos
I must admit I was thinking in terms of a piece of stiff wire, paperclip thickness or 1/16" welding rod and using a former to bend it around. The wobble on the way through can be cured by setting the hot loop up so it sticks through a "fence" and sliding the foam past it - think in terms of a hot wire "circular table saw or router table" type set up. If the loop is rigid enough and the foam slides on a solid surface against a solid guide fence you should get what you want. The only issue will be getting enough amps at a low voltage into the wire loop. A car type battery with some suitable bulbs arranged in a series-parallel arrangement to adjust the current comes to mind or a car battery charger.
 
DON'T try Ni-cads or NiMh - you might get a nasty surprise - I gather they don't like low resistance circuits and high currents, they could get hotter than the wire!
Keith
Les Jones 123/01/2012 17:42:35
2292 forum posts
159 photos
Hi Simon,
My understanding of what you are trying to produce is a piece of foam 10 mm dia and 100 mm long with 3 mm bamboo stick through the centre. If this is correct then what about inserting the bamboo into a larger diameter piece of foam then making a lathe like machine that rotates very slowly an having a hot wire cutter parallel with the axis. with the "lathe" rotating feed the toolpost holding the hot wire into the foam until it is 5 mm from the axis (Against a preset stop.) and and allowing it to rotate one revolution. A variation on this idea would be to make "lathe tool" from a "U" shaped strip of metal that was heated by the hot wire method. This would require you to modify a transformer to give a very low voltage at a high current. (Probably a one or two turn secondary of very thick wire.) The foam could then be turned like a normal lathe but a very low speed. Probably about 3 rpm.
One of the old fashioned instant soldering irons could provide the transformer. A suitable strip of metal could be the strips of metal that are in the groves of a windscreen wiper blade.
 
Les.
Billy Mills23/01/2012 19:06:40
377 forum posts
Thought that was more or less what I suggested earlier Les ! The bamboo is only there to add stiffness. Mike Cox has a nice hot wire cutter on his site, he uses a LV lighting ""Transformer"" to power the hot wire (probably rated around 12V @ 5A) .
 
It would be simple to mount the block onto a Cox style cutter with a vertical axle supported at both ends or to insert the axle into strips of wood at each end set the wire 5mm from the axle on a batten so that you can bring the wire into the block then turn it..
 
You can get dimmable LV lighting""transformers"" for a couple of quid from CPC. If you have a toroidal transformer then you can wind on some insulated wire to get whatever voltage you need.
 
Billy.
 

 
1 2 Next > Last >>

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Sign up to our Newsletter

Sign up to our newsletter and get a free digital issue.

You can unsubscribe at anytime. View our privacy policy at www.mortons.co.uk/privacy

Latest Forum Posts
Support Our Partners
cowells
Sarik
MERIDIENNE EXHIBITIONS LTD
Shopping Partners
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest

 

Donate

donate