Found Dreaming

So I was thinking today (I know, something is liable to burn up)... anyhow I have a pattern that is a little smaller than I would like for it to be. I am looking at maybe 0.0625" in total width so 0.03125" on each side would get me there. Rather than remake the pattern larger I got to thinking maybe a few coats of paint might do the trick.

From what I can tell a coat of spray paint is maybe 4 to 5 thousandths so I am thinking I can make up what I want with half a dozen or so good coats. Got three coats on today so tomorrow will do some more and hopefully the following day be able to try out the pattern to see if it made up what I was after.

Another thought I had but did not try (maybe next time) was to dust the pattern with fine sawdust, I have a lot of micro wood dust from cutting mdf on the router table. May just have to do some testing with this idea.

This growing of patterns would be very helpful with making up for shrink when making a reproduction part from an original though of course the owner of the original would have to be willing to let you paint it up. I suppose you could do a casting and add more layers of paint to not only get back to the original size but also go beyond so the next casting will come out the right size.

Use high build primer. Goes on twice as thick as regular paint.

Wayne

I have been using Rustolem 2x primer. It has a higher density of pigment. Never saw high build primer but that sounds like the ticket, will look for it. Do you know if they sell it at the big box stores is or this an auto body sort of thing?

Harry,

I've only seen it at the auto paint suppliers. Most towns have them. Ebay would also be a good place to buy it if you're having trouble finding it in your area.

David

Don't know about in the US but motor factors in the UK carry it in spray cans. Usually a yellow high build and works very well on loosing body re-work marks. It has a very matte texture when dry so will need some sanding and build up with a gloss after.

This could be a stupid idea(never stopped me before)but couldn't that much enlargement be accomplished with a little excessive rapping of the pattern before withdrawing it?
Don

Thanks guys, I will definitely look for the high build primer for future use. For this pattern I will just keep putting on coats of what I have and see if I can bring it up to size. If not then I will just cut another a little larger.

Don, that is common but I am looking for a very consistent difference in size over a lot of parts produced by the pattern. Also I tend to get some breaking if I try to force a pattern too much back and forth that will make cracks in the sand and of course flashing to match the cracks on the part.

The idea is sound though and handy to remember if you just need a little oomph on a single part.

Plastidip is VERY thick, available at most hardware and big box stores, and is plenty tough to ram against. Im thinking about using it on an engine valve cover Id like to reproduce with a custom image. All I can find are actual cast covers (obviously a pattern blank is not commercially availabe), so using one for a pattern would reproduce a dimensionally smaller casting. Im hoping to coat a junkyard cover with this stuff to allow for shrink.

It is tough but not hard right? I would think the sharp corners of the sand grains might try to dent and lock into the plastic. Maybe paint over it? Let us know how it works out.

Here in Nz we can get a high build 2 pack epoxy paint. I think it is called capraprime (SP) it is so hard after a few days that it will hold up to hand mixed concrete in a wheel barrow
The other thing that you cod use is epoxy glue thined down with solvent. that will not only make the pattern hard as all hell but it will help hold it together