Homebrew_PCBs

> Hi,
>
> I'm thinking about building a spray etcher. This has been discussed
> here before, but I haven't found an answer to my questions. I want
> to build the centrifugal type so that no pump is needed. Can anyone
> tell me how exactly these pick up the fluid at the bottom? Probably
> a picture? And the other thing I need to know is what speed is
> needed to spin the tube fast enough to spread the fluid.
>
> Regards
> Martin
>
>

--- In Homebrew_PCBs@yahoogroups.com, JanRwl@A... wrote:
> In a message dated 6/16/2004 3:33:32 PM Central Standard Time,
> atlantis7@g... writes:
> ...so that no pump is needed. Can anyone tell me how exactly these
pick up
> the fluid at the bottom?<<
> is this not an oxymoronic pair of statements? Wouldn't it be
a "pump" if it
> "picked up the fluid at the bottom"?
>
> Find yourself a discarded-but-working Water-Pic. There's a neat
little PUMP
> in there which is at least MOSTLY all-plastic, so might do for such
a thing.
>
>
> [Non-text portions of this message have been removed]

> Hello,
>
> I now you said you didn't want the pump. But I wonder why? A RULE
> brand pump for bilge duty in boats is less than 12 bucks, designed
> for occasional continuous use, designed for oil, gas, sludge, etc.
> and is cheap and easy to replace when/if necessary. Parts washer
> pumps from HF are another possibility.
>
> Container, pump, short length of tubing full of holes, problem
> solved, under 20 bucks, and likely under 4 hours. Simple, cheap,
> reliable, repairable. Works for me.
>
> Why make it harder?
>
> Ballendo
>
> --- In Homebrew_PCBs@yahoogroups.com, JanRwl@A... wrote:
>
>>In a message dated 6/16/2004 3:33:32 PM Central Standard Time,
>>atlantis7@g... writes:
>>...so that no pump is needed. Can anyone tell me how exactly these
>
> pick up
>
>>the fluid at the bottom?<<
>>is this not an oxymoronic pair of statements? Wouldn't it be
>
> a "pump" if it
>
>>"picked up the fluid at the bottom"?
>>
>>Find yourself a discarded-but-working Water-Pic. There's a neat
>
> little PUMP
>
>>in there which is at least MOSTLY all-plastic, so might do for such
>
> a thing.
>
>>

> I agree with Ballendo,
> In regards to amount of hours spent building any spray etching
> machine, you will save far more time (and possibly money)trying
> to by off the shelf parts, rather than go through the R+D and
> construction of an alternative spraying technique. The concept
> may look simple, but making your contraption into a practical
> work of art is a totally different ball game. Try searching the
> Homebrew_PCBs archives, as there was some discussion possible
> pumps to use. The brands Shurflo and Flojet come to mind, which
> are available from most caravan equipment suppliers. Prices are
> on the order of US$50.
>
>
> Adam

> On Thu, 17 Jun 2004 12:02:13 +1000, Adam Seychell
> <a_seychell@...> wrote:
>
>
>>I agree with Ballendo,
>>In regards to amount of hours spent building any spray etching
>>machine, you will save far more time (and possibly money)trying
>>to by off the shelf parts, rather than go through the R+D and
>>construction of an alternative spraying technique. The concept
>>may look simple, but making your contraption into a practical
>>work of art is a totally different ball game. Try searching the
>>Homebrew_PCBs archives, as there was some discussion possible
>>pumps to use. The brands Shurflo and Flojet come to mind, which
>>are available from most caravan equipment suppliers. Prices are
>>on the order of US$50.
>>
>>
>>Adam
>
>
> what i would fear with a pump setup is the fixed position of the nozzles -
> how do you get a even etch?

>
> Here are some early pictures I've taken of the tank during
> construction.
>
>

> In a message dated 6/17/2004 1:45:10 AM Central Standard Time,
> a_seychell@... writes:
> http://members.optusnet.com.au/~eseychell/pictures_of_etching_machine/IMGP1384
> ..jpg
> AH, you do not SUBMERGE your boards in etchant! So my "bubble suggestion" is
> irrelevant. Your nice spray method would be super, but this requires a pump
> a bit more sophisticated than most home-hobbiests would feel fiscally
> appropriate.

> Hi,
>
> I'm currently building my own spray etcher of the rotating
> perforated tube type. The most difficult problem is to get the fluid
> up that tube. Does anyone know what kind of mechanism commercial
> spray etchers like the ones from Bungard use?
>
> Regards
> Martin
>

>Hi,
>
>I'm currently building my own spray etcher of the rotating
>perforated tube type. The most difficult problem is to get the fluid
>up that tube. Does anyone know what kind of mechanism commercial
>spray etchers like the ones from Bungard use?
>
>Regards
>Martin

> >Hi,
> >
> >I'm currently building my own spray etcher of the rotating
> >perforated tube type. The most difficult problem is to get the

> >up that tube. Does anyone know what kind of mechanism commercial
> >spray etchers like the ones from Bungard use?
> >
> >Regards
> >Martin
>
> The one I have is having a small plate that basically would "close"
> the tube but this plate is having three holes in it. Can't tell

> memory wehter these are just holes or if they are drilled with an
> angle to form some sort of propeller as Stefan sugested.
>
> IMHO it's not too important as long as some fluid can get in. The
> plate moreover seems to serve as a way to even limitt the amount of
> fluid that otherwise would go up the tube. The problem here is that
> yuo need a surprisingly powerfull motor to drive the tube and I can
> imagine that having no plate there would simply make the tube

> less quickly leading to a less intense spray effect. These are just
> speculations on my end. I never did eny experimenting yet.
>
> Markus

> What diameter does the tube approximately have?

----- Original Message -----
From: "cruizzer77" <atlantis7@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, July 21, 2004 12:30 PM
Subject: [Homebrew_PCBs] Spray etcher


> Hi,
>
> I'm currently building my own spray etcher of the rotating
> perforated tube type. The most difficult problem is to get the fluid
> up that tube. Does anyone know what kind of mechanism commercial
> spray etchers like the ones from Bungard use?

A peristaltic pump might work. It has the advantage that the etchant doesn't
come into contact with any moving parts.

Leon

On Wed, 21 Jul 2004 13:35:01 -0000, cruizzer77 <atlantis7@...> wrote:

> Thanks for your replies!
>
> I tried the one with the propeller, mounted a small cpu fan
> propeller on the bottom of the tube and the upper part of a half-
> liter fanta bottle over it to form a kind of funnel. The rotating
> direction was correct but there happened _nothing_ when I sped it up
> to 5000 turns (I used water to test it). By the way I simply used a
> drill with a flexible to drive it. The problem is that I'm using a
> KRH M20 electrician's installation tube with an outside diameter of
> 20mm which is too small to fit any propeller inside. But the idea
> with the 3 holes sounds interesting, I imagine that the holes are
> drilled with an angle. What diameter does the tube approximately
> have?
>
> Regards
> Martin

>> What diameter does the tube approximately have?
>
> Out of my memory I'd say ~2.5 - 3 cm. There are obviousely holes
> within the tube and they go around it in a spiral form aparently to
> smothen the spraying process.
>
> I honestly can't tell at the moment (not at home) wether the holes in
> the bottom plate have an angle or not.
>
> Markus

> Hi,
>
> I'm currently building my own spray etcher of the rotating
> perforated tube type. The most difficult problem is to get the

> up that tube. Does anyone know what kind of mechanism commercial
> spray etchers like the ones from Bungard use?
>
> Regards
> Martin

> ----- Original Message -----
> From: "cruizzer77" <atlantis7@...>
> To: <Homebrew_PCBs@yahoogroups.com>
> Sent: Wednesday, July 21, 2004 12:30 PM
> Subject: [Homebrew_PCBs] Spray etcher
>
>
>> Hi,
>>
>> I'm currently building my own spray etcher of the rotating
>> perforated tube type. The most difficult problem is to get the fluid
>> up that tube. Does anyone know what kind of mechanism commercial
>> spray etchers like the ones from Bungard use?
>
> A peristaltic pump might work. It has the advantage that the etchant
> doesn't
> come into contact with any moving parts.
>
> Leon
>

> Hi MArtin,
>
> I'm not sure I follow your question. It seems that the rotating wand
> would be like a dishwasher spray wand ? it would have many different
> holes and they would be angled so the more pressure, the faster it
> would spin ?
>
> When you mentioned spinning, the first thing that came to my mind
> would be to have a shaft that came out of the enclosure
> and that would have a motor on it.
>
> But that would mean a circular spray pattern if the want rotates in a
> circle.
>
> dunno what your project looks like.
>
> But, I would be careful about having ANYTHING under pressure that was
> NOT in a secondary containment vessle of some sort. If a fitting or
> tube were to leak, there should be some means of containing the spray
> as well as the fluid.
>
> I would not like any Xenomorph blood on my carpet.
>
> Dave

>
> No, no wands here.
> (didn't even know the arm in the dishwasher is a wand, thought a

> only
> used by wizards ;-) )
>
> a rotating tube, and centrifugal force.
> like
> <http://www.megauk.com/cgi-bin/mega/lp.pl?

> <http://www.computronics.com.au/rota-spray/>
>
> ST
>
>
> > Hi MArtin,
> >
> > I'm not sure I follow your question. It seems that the rotating

> > would be like a dishwasher spray wand ? it would have many

> > holes and they would be angled so the more pressure, the faster

> > would spin ?
> >
> > When you mentioned spinning, the first thing that came to my mind
> > would be to have a shaft that came out of the enclosure
> > and that would have a motor on it.
> >
> > But that would mean a circular spray pattern if the want rotates

> > circle.
> >
> > dunno what your project looks like.
> >
> > But, I would be careful about having ANYTHING under pressure

> > NOT in a secondary containment vessle of some sort. If a

> > tube were to leak, there should be some means of containing the

> > as well as the fluid.
> >
> > I would not like any Xenomorph blood on my carpet.
> >
> > Dave

> Yes these are exactly the machines I had in mind. The Bungard Jet 34
> is the archetype of these rotary spray etchers, but of course
> detailed pictures are nowhere to be found, they don't want people to
> imitate their machines, do they...
>
> Regards
> Martin

>I'm convinced the photo i linked to wasn't shot at that angle by accident.
>The corner is obstructing view of the tube...
>
>But if one really wants to copy it in large-scale they will simply buy a
>unit.

>I wonder who has the patent.

>
> Bungard, but since it dates back to the sixties I figure the patent
> protection is meanwhile void. I'm however not experienced, that

> don't know if a patent is protecting "forever" or if it's only
> effective for some years.
>

> Thanks for your replies!
>
> I tried the one with the propeller, mounted a small cpu fan
> propeller on the bottom of the tube and the upper part of a half-
> liter fanta bottle over it to form a kind of funnel. The rotating
> direction was correct but there happened _nothing_ when I sped it up
> to 5000 turns (I used water to test it). By the way I simply used a
> drill with a flexible to drive it. The problem is that I'm using a
> KRH M20 electrician's installation tube with an outside diameter of
> 20mm which is too small to fit any propeller inside. But the idea
> with the 3 holes sounds interesting, I imagine that the holes are
> drilled with an angle. What diameter does the tube approximately
> have?
>
> Regards
> Martin
>
>
>
> --- In Homebrew_PCBs@yahoogroups.com, Markus Zingg <m.zingg@n...>
> wrote:
>
>>>Hi,
>>>
>>>I'm currently building my own spray etcher of the rotating
>>>perforated tube type. The most difficult problem is to get the
>
> fluid
>
>>>up that tube. Does anyone know what kind of mechanism commercial
>>>spray etchers like the ones from Bungard use?
>>>
>>>Regards
>>>Martin
>>
>>The one I have is having a small plate that basically would "close"
>>the tube but this plate is having three holes in it. Can't tell
>
> from
>
>>memory wehter these are just holes or if they are drilled with an
>>angle to form some sort of propeller as Stefan sugested.
>>
>>IMHO it's not too important as long as some fluid can get in. The
>>plate moreover seems to serve as a way to even limitt the amount of
>>fluid that otherwise would go up the tube. The problem here is that
>>yuo need a surprisingly powerfull motor to drive the tube and I can
>>imagine that having no plate there would simply make the tube
>
> rotate
>
>>less quickly leading to a less intense spray effect. These are just
>>speculations on my end. I never did eny experimenting yet.
>>
>>Markus
>
>
>
>
>
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs
> Yahoo! Groups Links
>
>
>
>
>
>

> If you place a spinning tube in water it will form a pump BUT the water
> will take the route of least resistance - straight back out the end of
> the tube! What you need to do is stop the water from flowing back out
> the tube. If you block the end of the tube apart from a hole in the
> centre the water will be sucked up the hole then forced to the outside
> of the tube. Now the only place for it to go is upwards. To work for
> spray etching you will probably need a fairly large diameter tube
> (50mm?) and a reasonable speed.
>
> Les

> To work for
>spray etching you will probably need a fairly large diameter tube
>(50mm?) and a reasonable speed.

> --- In Homebrew_PCBs@yahoogroups.com, Markus Zingg <m.zingg@n...>
> wrote:
>
>>Bungard, but since it dates back to the sixties I figure the patent
>>protection is meanwhile void. I'm however not experienced, that
>
> said I
>
>>don't know if a patent is protecting "forever" or if it's only
>>effective for some years.
>>
>
>
> 17 years
>

> Does the yahoo groups "search archive" feature search the entire

> of the messages ? I coulnd't find this message using the yahoo

> All the messages are stored, but it seems they cannot all be

> had to search for this message from the email folder on my home PC.

>>Does the yahoo groups "search archive" feature search the entire
>
> hystory
>
>>of the messages ? I coulnd't find this message using the yahoo
>
> search.
>
>>All the messages are stored, but it seems they cannot all be
>
> searched. I
>
>>had to search for this message from the email folder on my home PC.
>
>
>
> Yahoo does indeed search on one keyword, but only 250 records at a
> time and then reports the results for those 250 posts.
>
> Since your search showed post 1561 and we are on post 6,383 then you
> would to hit the NEXT button quite a few times !
>

>
> I still cannot get the point of a spray etcher. Someone could direct
> me
> to a site or something I can get more info? I'm really curious about this
> one.
>

> Phil wrote:
> > --- In Homebrew_PCBs@yahoogroups.com, Markus Zingg

> > wrote:
> >
> >>Bungard, but since it dates back to the sixties I figure the

> >>protection is meanwhile void. I'm however not experienced, that
> >
> > said I
> >
> >>don't know if a patent is protecting "forever" or if it's only
> >>effective for some years.
> >>
> >
> >
> > 17 years
> >
>
> we had patent discussion long time ago on this group.
> see message
> http://groups.yahoo.com/group/Homebrew_PCBs/message/1561
>
> Does the yahoo groups "search archive" feature search the entire

> of the messages ? I coulnd't find this message using the yahoo

> All the messages are stored, but it seems they cannot all be

> had to search for this message from the email folder on my home PC.

> Well this is interesting. The original patent paper clearly states
> that the etchant is pumped up the tube using a sprial mounted inside
> the tube. This sounds reasonable to me but unfortunately will be
> close to impossible to fabricate such a spiral. Somebody who has at
> least a middle-sized lathe could probably try to turn it out of a
> plastic bar, similar to turning a thread. I think I'll try the 3-
> hole type next.
>
> Regards
> Martin
>

> Well this is interesting. The original patent paper clearly states
> that the etchant is pumped up the tube using a sprial mounted

> the tube. This sounds reasonable to me but unfortunately will be
> close to impossible to fabricate such a spiral. Somebody who has at
> least a middle-sized lathe could probably try to turn it out of a
> plastic bar, similar to turning a thread. I think I'll try the 3-
> hole type next.
>
> Regards
> Martin
>
>
> Actually, sepending on the speed of the twists, or twists per inch,

> A spray etcher is faster than most other methods, because it uses a

> of force/agitation. It is basically a set of nozzles spraying

> at a board, and the nozzles move so it is distributed evenly.
> You get etch times around one minute or even less with it.
>
> If you etch in a bowl the "used" etchant will sit close to the

> the PCB, prolonging etch time. you will want to use some sort of

> (like moving the board or bubbles) to speed it up. But even with a

> agitation you don't get the speed of spray etching. (dunno why)
>
>
> ST

> Actually, sepending on the speed of the twists, or twists per inch,
> one can take PVC and just twist it into shape like a wrought iron
> railling spindle. Or, one could hand file a part without too much
> difficulty.
>
> Dave
>
>

> I think I read about surface tension of the etchant and exposure of
> the coppper being different if it was submerged and bubbled and
> sprayed. IIRC, spraying acutally allowed the etchant to be removed
> down to the copper whereas the think film of etchant with bubbling
> never really did.
>
> Dave
>

> Well this is interesting. The original patent paper clearly states
> that the etchant is pumped up the tube using a sprial mounted

> the tube. This sounds reasonable to me but unfortunately will be
> close to impossible to fabricate such a spiral. Somebody who has

> least a middle-sized lathe could probably try to turn it out of a
> plastic bar, similar to turning a thread. I think I'll try the 3-
> hole type next.
>
> Regards
> Martin
>
>
>
>
>
>
> --- In Homebrew_PCBs@yahoogroups.com, Adam Seychell
> <a_seychell@y...> wrote:
> > Phil wrote:
> > > --- In Homebrew_PCBs@yahoogroups.com, Markus Zingg
> <m.zingg@n...>
> > > wrote:
> > >
> > >>Bungard, but since it dates back to the sixties I figure the
> patent
> > >>protection is meanwhile void. I'm however not experienced,

> > >
> > > said I
> > >
> > >>don't know if a patent is protecting "forever" or if it's only
> > >>effective for some years.
> > >>
> > >
> > >
> > > 17 years
> > >
> >
> > we had patent discussion long time ago on this group.
> > see message
> > http://groups.yahoo.com/group/Homebrew_PCBs/message/1561
> >
> > Does the yahoo groups "search archive" feature search the entire
> hystory
> > of the messages ? I coulnd't find this message using the yahoo
> search.
> > All the messages are stored, but it seems they cannot all be
> searched. I
> > had to search for this message from the email folder on my home

> Yes that's it! The 3-hole version works basically. I actually did
> angle the holes a bit and at 7'000 rpm the water splashed out of the
> holes up to about 5 cm from the bottom. The drill I used to drive
> cannot spin faster, so it seems as if I needed a high speed motor.
> Once this is done I will probably also try a base plate with only
> one hole in the middle. Does someone have an idea from what kind
> of "everyday device" a motor with a speed range up to 10'000 to
> 12'000 rpm could be salvaged? I think not even a vacuum cleaner
> spins that fast, apart from the fact that those motors are
> considerably large. Another problem will be that my bearings in the
> condition being will not withstand those high rpms.
>
> Regards
> Martin
>

>Well this is interesting. The original patent paper clearly states
>that the etchant is pumped up the tube using a sprial mounted inside
>the tube. This sounds reasonable to me but unfortunately will be
>close to impossible to fabricate such a spiral. Somebody who has at
>least a middle-sized lathe could probably try to turn it out of a
>plastic bar, similar to turning a thread. I think I'll try the 3-
>hole type next.

> On Thu, 22 Jul 2004 13:36:25 -0000, cruizzer77 <atlantis7@g...>

>
> > Yes that's it! The 3-hole version works basically. I actually did
> > angle the holes a bit and at 7'000 rpm the water splashed out of

> > holes up to about 5 cm from the bottom. The drill I used to drive
> > cannot spin faster, so it seems as if I needed a high speed

> > Once this is done I will probably also try a base plate with only
> > one hole in the middle. Does someone have an idea from what kind
> > of "everyday device" a motor with a speed range up to 10'000 to
> > 12'000 rpm could be salvaged? I think not even a vacuum cleaner
> > spins that fast, apart from the fact that those motors are
> > considerably large. Another problem will be that my bearings in

> > condition being will not withstand those high rpms.
> >
> > Regards
> > Martin
> >
>
> smaller DC motors (like for model building) are build to spin that

> For higher
> power look at grinders, angle grinders and straight grinders that

> You have good chances a "universal motor" (the kind with carbon

> is that fast,
> where a "squirrel cage" motor without brushes is surely not.
> You can also buy a $10 "dremel clone" they have a 12k or so 100W

> ball bearings,
> basically nothing else.
> Model building motors (which in fact are simply small industrial

> dc motors
> like Johnson and mabuchi makes) can obviously be bought in model

> shops.
> (look for "speed" 550 or 600). You can find a 550 or 600 in every

> handheld
> vacuum cleaner.
> I'm not sure about other universal motors like big vacuums, or

> drills without
> the gearing, but looking at a power drill output and contemplating
> the gearing ratio it might well be enough on the motor.
>
> ST

>>I think I read about surface tension of the etchant and exposure of
>>the coppper being different if it was submerged and bubbled and
>>sprayed. IIRC, spraying acutally allowed the etchant to be removed
>>down to the copper whereas the think film of etchant with bubbling
>>never really did.
>>
>>Dave
>>
>
>
> must be the cause. moving the board seems to work ok, and it is zero-mist
> also.
>
> I wonder what a ultrasonic transducer would cause?
> I mean it also rips off the etchant, doesn't it? the question is if the
> resist
> would survive (anyone having a ultrasonic please put a board with resist
> in and tell us).
>
> ST
>
>
>
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs
> Yahoo! Groups Links
>
>
>
>
>
>

--- In Homebrew_PCBs@yahoogroups.com, Les Newell <les@l...> wrote:
> Just make sure your tank is compatible with your etchant - Ferric
will
> eat stainless!
>
> Les
>
> Stefan Trethan wrote:
> >>I think I read about surface tension of the etchant and exposure
of
> >>the coppper being different if it was submerged and bubbled and
> >>sprayed. IIRC, spraying acutally allowed the etchant to be
removed
> >>down to the copper whereas the think film of etchant with
bubbling
> >>never really did.
> >>
> >>Dave
> >>
> >
> >
> > must be the cause. moving the board seems to work ok, and it is
zero-mist
> > also.
> >
> > I wonder what a ultrasonic transducer would cause?
> > I mean it also rips off the etchant, doesn't it? the question is
if the
> > resist
> > would survive (anyone having a ultrasonic please put a board
with resist
> > in and tell us).
> >
> > ST
> >
> >
> >
> > Be sure to visit the group home and check for new Bookmarks and
files:
> > http://groups.yahoo.com/group/Homebrew_PCBs
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >

> Yes everything is made of plastic, both PVC and PP, except some
> screws which are A4 stainless which is acid resistant.
>
> Regards
> Martin

> On Thu, 22 Jul 2004 16:43:01 -0000, cruizzer77 <atlantis7@g...>

>
> > Yes everything is made of plastic, both PVC and PP, except some
> > screws which are A4 stainless which is acid resistant.
> >
> > Regards
> > Martin
>
>
> You sure the screws are resistant?
> I don't know about other etchants but my CuCl loves to eat

> lunch.
>
> ST

> Unfortunately I think you're right. I expected a material labelled
> as acid resistant to be resistant enough for etchant. As I can't do
> without screws I have to try and get plastic screws, but chances
> that I can buy PP, PE or PVC ones are small, these are usually made
> from PA which is again only halfways resistant.
>
> Regards
> Martin

> yea nylon is said to go bad in etchant..
>
> (By the way rubber, like in bike inner tires, is resistant to

> it in my tank as a rubber band.)
>
> When i asked for plastic screws some time ago someone here

> source
> mentioning you can get many types of plastic there.

> According to every website I have looked at, acrylic has good resistance
> properties to acids and alkalides, and specifically copper chloride and

> chloride so i cannot see why it would not be safe to use, unless it is the

> to stick the acrylic sheets together?

> D. Gareth Hughes wrote:
>
> According to every website I have looked
> at, acrylic has good resistance properties
> to acids and alkalides, and specifically
> copper chloride and ferric chloride so i
> cannot see why it would not be safe to use,
> unless it is the glue used to stick the
> acrylic sheets together?
>

--- In Homebrew_PCBs@yahoogroups.com, "Tim Gibbs" <timgibbs@...> wrote:
>
> Hi All,
>
> A possible explanation for the acrylic crazing is a combination of using
> H2O2 and heat.
>
> Benzyl peroxide is used as a initiator for the setting reaction in dental
> acrylic used in dentures.
>
> Dentures are made using a lost wax casting processes where the denture is
> waxed up and then invested in plaster. The mold is warmed up and the wax is
> removed. A mixture on partly processed acrylic as a fine powder is mixed
> with liquid monomer to form a dough usually with benzyl peroxide as the
> initiator. A little heat is applied and the dough polymerises to form the
> acrylic.
>
> Patients are advised not use bleach on their dentures.
>
>
>
> Cheers
>
> Tim
>
>
> Is it a problem with peroxide then?
>
> 'Cause I had a commercial acrylic bubble
> tank that was used for years without problem.
> Then after switching to CuCl (regenerated
> with 40 weight H2O2) it crazed and went
> brittle in about 6 months.
>
>
>
>
>
> [Non-text portions of this message have been removed]
>