resin casting bubble/pits accepted level.

[propologist]

Might be a stupid question but I wanted to ask about acceptable pits/craters etc. in casts. As I look though many of the props that are cast etc, some are look great at distance and then looking at more detail they look pitted or orange peeled.
What's the acceptable level for good casts ? I would assume no pits etc. would be ideal but I often see worse in runs and other places that seem to be ok. let me know what you guys think and anyone have some examples .

 

[exoray]

Depends on the person doing the casting, there is a lot of crap sold in this community that deserves the garbage can, and there are a lot of very good artist that make fantastic castings as well...

Me personally, I am for nothing larger than say a small number of pin hole bubbles, any significant imperfections and they get sold as 2nds... I get told time and time again that my 2nds are not 2nds but every bit as good as the normal, my 3rds go right in the trash even though I have seen worse sold in this community, I refuse to sell garbage castings...

 

[Eaglewood]

Depends on the person doing the casting, there is a lot of crap sold in this community that deserves the garbage can, and there are a lot of very good artist that make fantastic castings as well...

Me personally, I am for nothing larger than say a small number of pin hole bubbles, any significant imperfections and they get sold as 2nds... I get told time and time again that my 2nds are not 2nds but every bit as good as the normal, my 3rds go right in the trash even though I have seen worse sold in this community, I refuse to sell garbage castings...

WELL SAID!!!!thumbsup

 

[defstartrooper]

Anything over a pinhole size is either someone lazy, someone who doesn't care what they send as long as they're paid, or someone that has no clue.

 

[BrundelFly]

There is just no excuse for mass airbubbles.

 

[propologist]

thanks guys , I can see experience being key and not to sell crap..lol

 

[exoray]

thanks guys , I can see experience being key and not to sell crap..lol

Technique is the key, not experience... There are a ton of several year 'experienced' casters out there that still make Swiss cheese and cottage cheese castings, while some newbie comes along with crisp clean castings...

I believe you will find that creating good castings starts with the mold design and a well thought out process, the entire process from start to finish... Many people are more interested in penny pinching, cutting corners and rushing to turn a quick buck...

 

[ONEYE]

Acceptable to me would be less than 10% of the total surface.

 

[tango'd fett]

The quality of resin you use makes a difference as well ,some of the cheap stuff comes out awful sometimes. Although as said mold design and molding technique do make a big difference too. Polyurethane is the best to use and if you want to emliminate airholes completely the only way to achieve that is pressure casting and degassing the resin beforehand. I have also heard that rotocasting is a good way to eliminate bubbles too ...or did i hear wrong !!:confused

 

[exoray]

Acceptable to me would be less than 10% of the total surface.

Wow you are pretty generous...

if you want to emliminate airholes completely the only way to achieve that is pressure casting and degassing the resin beforehand.

You can eliminate 99.9% of all surface bubbles without doing either if you devote the time an effort... A lot of it will be what you are casting and what is involved in filling the mold...

 

[tango'd fett]

tell us then o master , tell us )

 

[ONEYE]

Wow you are pretty generous...

Too generous?

 

[propologist]

Technique is the key, not experience... There are a ton of several year 'experienced' casters out there that still make Swiss cheese and cottage cheese castings, while some newbie comes along with crisp clean castings...

I believe you will find that creating good castings starts with the mold design and a well thought out process, the entire process from start to finish... Many people are more interested in penny pinching, cutting corners and rushing to turn a quick buck...

Yeah I can see that. I'm trying to learn the process BEFORE i start doing anything. I have been capturing pictures , reading a ton of threads and internet things and comparing pictures of things I have seen here.
I like the rotocasting and it seems very doable with the right set up. I would guess that and degassing would kill many of the problems.

 

[exoray]

tell us then o master , tell us )

There is not one particular way to do it... It varies by application, mold design, what you are casting, way to many variable to state an absolute way to do it...

For example I cast small light bars, because it's a finished product with no additional paint or prep work there is no margin for surface air bubbles... To accomplish this I use a slower setting resin, massage the mold, and basically run/brush a tool over known problem areas in the mold once filled to work out trapped bubbles... I also pour out my resin dosages ahead of time allow them time to naturally degas, before mixing, I then pay close attention while mixing to not introduce more air... I also try and avoid casting urethane in high humidity to help eliminate reactions with water in the air that will create voids... For larger castings, you can do a brush on 'gelcoat' type layer before the fill... Lots of other methods as well, powder the mold, rotating the mold the list could go on and on...

Too generous?

IMO for many castings yeah... I regularly toss castings for less...

I would guess that and degassing would kill many of the problems.

It works very well, but it also slows your cycle time, many people use the 2-3 minute kick urethane resins, 2-3 minutes (if you get that much time, form my experience you don't get that time unless your room temp is very cool) isn't much time to properly mix, degas and then pour while still giving the resin time to find it's way into the mold and level out before it starts to at best thicken...

 

[stormtrooperguy]

I think it depends a lot on how much you pay for it too.

If I'm buying a $20 resin blaster, I'll be really forgiving of imperfections.

If I buy a $200 resin blaster, not so much.

When I cast something, I just look at it and think "would I be happy getting this for whatever I charged for it". If I can honestly say that I'd be happy with it, I'm ok giving it out.

If there are any big bubbles / problems, I fix them before shipping. So take something like my clone DC-15s rifles: They take about 72oz liquid to fill, so I'm not casting them into the seconds pile unless it's unavoidable. If I have to spend 30 minutes doing cleanup before I ship it, so be it.

Oh, and like exoray is saying, there are a lot of things you can do. I brush in the "gelcoat" layer of resin first, tap the molds, powder the molds, all of that... the end result is a better product by far!

Similarly, I usually use resins that kick in 5 minutes or less, so there's not much time for degassing.

 

[Raffles]

If it takes me longer than 15 mins to fill them, there's too many.

 

[propologist]

I think it depends a lot on how much you pay for it too.

If I'm buying a $20 resin blaster, I'll be really forgiving of imperfections.

If I buy a $200 resin blaster, not so much.

When I cast something, I just look at it and think "would I be happy getting this for whatever I charged for it". If I can honestly say that I'd be happy with it, I'm ok giving it out.

If there are any big bubbles / problems, I fix them before shipping. So take something like my clone DC-15s rifles: They take about 72oz liquid to fill, so I'm not casting them into the seconds pile unless it's unavoidable. If I have to spend 30 minutes doing cleanup before I ship it, so be it.

Oh, and like exoray is saying, there are a lot of things you can do. I brush in the "gelcoat" layer of resin first, tap the molds, powder the molds, all of that... the end result is a better product by far!

Similarly, I usually use resins that kick in 5 minutes or less, so there's not much time for degassing.

yeah that makes good sense. I can see fixing any problems before tossing really.