How many instrument sets does your salon need? Plan the time between appointments
- 16 min reading time
The number of complete instrument sets your salon needs comes from your appointment schedule and the actual time until used instruments become correctly available again. It cannot be read from an autoclave's nominal capacity in litres. First count the sets occupied at the same time. Then identify how many appointments start before those sets have passed the full applicable reprocessing and release route. Only after that calculation should you choose between buying more sets, changing appointments or assessing additional appropriate processing capacity.
A set is not one pair of scissors or a random group of metal tools. It means the complete collection of reusable items needed for a defined treatment. Keep consumables and single-use items on a different stock list. An instrument returned from a client but waiting for cleaning does not count as ready stock. Nor does a completed machine cycle automatically establish that the individual set is cleared for the next client.
The three schedules below are explicitly hypothetical arithmetic examples. Their appointment times and return times are neither measured Fomos performance nor prescribed sterilisation periods. Whether a particular instrument requires cleaning, disinfection or sterilisation depends on the treatment, the type of contact, the original instrument instructions and the applicable professional rules. A barber shop, nail studio and piercing business should not be treated as if they shared one identical legal procedure.
1. Define a complete set for each treatment
Instead of writing down every tool in the building, make an inventory for each frequently booked service. Treatment A might require a particular nipper, tweezers and another reusable component. Treatment B may have a different composition. One pair of tweezers cannot be allocated to two sets required simultaneously. Where an instrument consists of detachable components, identify the parts needed for use and check whether the manufacturer allows their reprocessing. A set that is missing a piece, has been damaged or has failed inspection is not operationally complete even if the main tool remains in a drawer.
Divide the inventory into ready for use, still being processed and unavailable. The processing category includes everything from the dirty return to documented release; it is not restricted to the minutes when a steriliser is running. Unavailable includes damaged instruments, items held for assessment, incomplete sets and items for which the necessary safe process cannot be confirmed. This distinction stops a count of twenty loose instruments being mistaken for twenty fully usable treatment sets.
Record the purpose of each instrument as well. Contact with intact skin is not the same situation as contact with damaged skin, blood or another body fluid. The RIVM index of current Dutch hygiene guidance can help identify the relevant specific discipline. Its piercing guideline applies to that profession rather than being a universal manicure rule. Establish the correct instrument route for the service before assigning any turnaround duration to it.
2. Follow the complete journey back to availability
An appointment can finish while the set remains unavailable for a considerable period. Depending on the required method and the individual instrument, the route can include dirty return, appropriate cleaning, inspection, preparation and packaging where necessary, permitted disinfection or sterilisation where necessary, drying and cooling where relevant, evaluation and release. Internal movement between stations and waiting for an appropriate batch also consume real calendar time. They are not automatically included in the operating time displayed for a particular machine programme.
Observe a representative workday and note separate times for return of the last instrument in a set, completion of its preparation, actual start of an applicable programme and final readiness following the required checks. Also identify who performs each step. The professional treating the next customer may not be free to clean instruments at the same moment. If an external service processes instruments, collection, transport, handover and return windows must be accounted for. The planning input is the total time until valid availability, not a convenient catalogue cycle figure.
The CDC overview of sterilising practices explains, in the context of US healthcare, why preparation, packaging, loading, monitoring and a suitable process have to be considered together. It is technical background, not Dutch salon legislation. Follow the instructions for the actual instrument and machine and any applicable service-specific Dutch requirements when establishing what the complete route entails.
3. Count overlapping commitments rather than guessing a magic number
For the busiest relevant part of the diary, put each complete set on a separate line. Mark when an appointment begins and the later moment when that precise set has actually become ready again. Between those marks the set remains committed, even if direct use during the treatment takes only a few minutes. At each new appointment, count how many sets are still committed and how many fresh sets are needed now. The largest simultaneous requirement gives the calculated minimum for this stated scenario. It is not a standard number for every business.
A useful check is that ready sets immediately before an appointment minus sets needed for that appointment must not fall below zero. Between appointments add back only sets that have genuinely completed the relevant reprocessing, checks and release. A simple sheet can have columns for clock time, new appointments, committed sets, confirmed returns and remaining ready sets. This makes a hidden shortage visible without assuming that a larger chamber or a faster advertised programme will somehow resolve it.
Decide on extra cover separately from the minimum. There is no verified single reserve percentage that applies equally to hairdressing, nail treatments and piercing. Base contingencies on your own interruption history, how easy it is to replace a complete instrument set and the consequence of a delayed appointment. Spare items must meet the same suitability and processing conditions as ordinary items; an uncleared instrument does not become safe merely because your reservation system is under pressure.
4. Three fully hypothetical and checkable schedules
Case A — one operator. Assume four treatments using one identical set each, starting at 09:00, 10:00, 11:00 and 12:00. Set A is used at 09:00, B at 10:00 and C at 11:00. Solely for this numerical example, suppose set A has completed every applicable stage and is released at 11:30. It can then be allocated to the 12:00 treatment, so three complete sets suffice for those four appointments. If A is not released until 12:15, the 12:00 booking needs a fourth set or a schedule change. That difference is caused by the return time, not by autoclave volume.
Case B — two operators working in parallel. Both operators each start one set at 09:00, 10:00 and 11:00. Six distinct sets have therefore been committed before any assumed return. Suppose, for the illustration only, that both 09:00 sets are properly released at 11:45. They can cover two new appointments at 12:00 and the minimum for this particular schedule is six sets. If their release moves to 12:30, those two noon appointments require eight sets or a rescheduled start. Neither number is a claim about a Foster machine's real throughput.
Case C — a processing window is interrupted. One operator has five visits beginning at 09:00, 10:00, 11:00, 12:00 and 13:00. Assume that no used set is released again before 16:00, perhaps because the next appropriate processing window is later in the day. Then five ready complete sets must already be available before the first visit. Adding a visit at 14:00 makes that six. The hypothetical delay could also arise from a separate external handover or staffing gap; it does not prescribe any technical treatment duration.
| Illustrative case | Uses before first return | Assumed release | Result |
|---|---|---|---|
| A: one operator | 09:00, 10:00, 11:00 | A at 11:30 | 3 sets; A reused at 12:00 |
| B: two operators | 2 × 09:00, 2 × 10:00, 2 × 11:00 | 2 sets at 11:45 | 6 sets; both return at 12:00 |
| C: delayed processing | five appointments, 09:00–13:00 | none before 16:00 | 5 sets ready beforehand |
These are planning calculations, not measured sterilisation results. Substitute your actual appointment times and full, verified return-to-use times. Where treatments need different sets, calculate the shared scarce component separately. Where a set is rejected because an item is damaged or the reprocessing result is unresolved, remove it from the ready stock and recalculate. There is no need to invent temperatures, cycle lengths or packs per tray to apply this arithmetic.
5. Find the stage that is actually limiting flow
Before buying a second appliance, examine where the sets are waiting. A queue of dirty returns often points to a preparation or staffing constraint rather than chamber capacity. A queue of correctly prepared sets awaiting a compatible permitted load suggests a different issue. Sets waiting for review, cooling or release after the machine has finished show that more machine volume alone may not help. Measure waiting time by stage so the investment is directed at the actual cause rather than at the most conspicuous appliance.
Four timestamps per set are often enough for initial analysis: return from treatment, end of required preparation, end of the equipment stage if applicable, and actual release. Do not add an imaginary sterilisation stage to an instrument for which the correct treatment route does not require sterilisation. Consumables that are single-use leave the reusable flow. After a representative week compare how often the next client lacked a ready set and whether the constraint was preparation, equipment, personnel or verification.
Physical instrument features matter too. Long, hollow, assembled or delicate instruments may need particular preparation and a compatible programme. A batch is appropriate only when the instructions and permitted configurations fit all its contents. Filling empty-looking space is not an adequate loading criterion. Packaging, weight distribution, exposure of surfaces and circulation of the sterilising medium must follow the validated manufacturer instructions; you cannot calculate safe sets per cycle from nominal litres alone.
6. More sets, a different diary or different equipment?
These are three distinct decisions. Additional complete sets increase the stock available during long return windows. A better distribution of appointments can reduce peaks when several services require a rare shared instrument. Greater suitable processing capacity only addresses a bottleneck located at that stage and only when the load and programme have actually been assessed as compatible. Buying another machine does not automatically solve a lack of staff for cleaning. Buying another pair of tweezers cannot by itself remove an equipment constraint.
Compare more than purchase prices. Spare sets involve subsequent processing, inspection, storage, deterioration and eventual replacement. Changing appointment patterns may affect booking choices. Equipment needs space, permitted installation, competent operators, maintenance, test arrangements and accurate documentation. The operator still needs a suitable programme for every actual type of load. The statement 'twelve litres is larger than eight' does not establish that the relevant sets will return quickly enough.
At Prohaar the Fomos Foster 8 L with printer and Fomos Foster 12 L with printer provide two concrete models to assess. Their current listings describe five sterilisation programmes, two test programmes, three supplied trays, a thermal printer and USB records. The programme tables include both Class B and Class S entries. Those are listed equipment features, not evidence of a universal number of instrument sets per load or a complete measured turnaround time.
7. Interpreting the Foster 8 and 12 litre comparison
The larger chamber becomes relevant only when your analysis shows that a larger appropriately permitted load could relieve the actual bottleneck. The 8 L product description states approximately Ø 170 × 320 mm for its chamber; the 12 L listing states approximately Ø 200 × 350 mm. The original Foster 8L/12L manual, revision 202401A, specifies Ø 200 × 358 mm for 12 L, so its depth differs from the shop listing. Check the version supplied with the machine rather than treating either 350 or 358 mm as a guaranteed usable package length. Chamber dimensions do not equal safe packaged instrument dimensions.
Measure the complete set, including any packaging, not only the longest loose instrument. Wrappers, holders and trays occupy space; the load must suit the required programme. Three supplied trays are not a confirmed number of instrument sets per cycle. Read the original Foster 8L/12L manual, revision 202401A, and compare it with the edition and device identification supplied with your unit. Chamber dimensions and tray counts do not replace a permitted loading configuration or assessment of the entire return-to-use process.
Read both the instrument instructions and the appliance instructions before estimating capacity. If instrument positioning, packaging or programme compatibility remains unclear, obtain a model-specific assessment from an authorised supplier or service partner rather than running an improvised load test. Prohaar's earlier Foster 8 L delivery checklist concerns supplied accessories; this article addresses the number of complete ready sets required at defined appointment times.
8. Use a practical weekly planning sheet
A basic sheet should record the type of service, starting time, operator, set identifier, ready status before use, dirty return and eventual release. Add a field naming the correct processing route for that instrument and service. It is a schedule, not a place to invent a chemical recipe or universal autoclave setting. Responsibilities should be explicit: who issues a set, who receives the used instruments, and who is permitted to release the correctly processed items under the studio's procedures.
Run the sheet through a busy but representative week. Mark delays such as a missing nipper, double-booked tweezers, unexpected package damage, staff absence, unavailable equipment or postponed review. Don't merely report that two sets were missing. Record when and why: one isolated one-hour peak may be better addressed by a spare set, while a systematic delay after every treatment calls for a process investigation.
Distinguish two findings: the calculated minimum stock that would cover the observed schedule and the separate allowance justified by plausible disruptions. Never shorten the return window on paper by omitting a required check or using an unsuitable faster programme. If equipment capacity is the demonstrated constraint, compare the autoclaves available at Prohaar against the actual instrument requirements. Check the current product details and availability at the time of ordering.
9. Contingency stock without taking shortcuts
If an operator, cleaning facility or machine becomes unavailable, a spare may bridge part of the gap, but the required treatment route cannot be skipped. Depending on the service and applicable guidance, reducing bookings, rearranging appointments or selecting genuinely suitable single-use instruments may be preferable to relying on an unusable reserve.
An unclear cycle result, damaged packaging or an instrument whose instructions do not match the chosen process requires assessment according to the relevant professional procedure. The mere passage of time is not a valid substitute for release. The CDC material on process monitoring helps explain these distinct concepts in a US healthcare setting. It does not make those healthcare rules automatic legal obligations for every Dutch salon. Apply the current Dutch sources for your particular service and the exact appliance and instrument manuals.
Frequently asked questions
How can I find the minimum before I know a full machine duration?
You can count the peak number of simultaneously committed sets, but a whole-day result needs reliable return-to-ready times. Record appointments alongside the actual moments when representative sets are released. Measure the unknown stage or establish it through the applicable approved workflow; do not borrow a cycle time from another machine.
Can the same set serve two consecutive clients?
Only if every required reprocessing, assessment and release stage has actually been completed before the second use. Back-to-back bookings do not establish this. If the complete return window is unknown or too long, plan another ready set or alter the order of appointments.
Do two operators always require twice as many sets?
Not automatically. Two simultaneous appointments using the same set definition need two separately ready sets. Subsequent demand depends on the timing of the next starts, different treatment requirements and when earlier sets are genuinely released.
How many instrument sets fit a Foster 8 or 12 litre machine?
Nominal litres do not give a reliable count. The actual instruments, packaging, trays, placement, permitted load and suitable programme must be checked against instructions for the delivered machine and each instrument. Three supplied trays are not proof of three complete treatment sets per cycle.
Is a Class B programme always the fastest choice for my diary?
No. The correct programme is determined by the permitted instrument and load, not an available appointment gap. Foster listings include Class S programmes as well. Choosing an unsuitable programme to shorten waiting time is not an acceptable planning measure.
Should damaged or unreleased instruments count towards stock?
No. Keep them out of ready stock pending the necessary assessment and action. A shortage in the appointment diary cannot change the instrument's actual status. Count only complete sets that have properly become available.
Does this counting method apply identically to barbers and piercers?
The scheduling arithmetic can be used across services, but instrument handling requirements are not identical. Check each discipline's applicable Dutch rules and the relevant instrument instructions. The RIVM piercing guidance is specific to piercing rather than a general manicure law.
Prohaar Magazine editorial team · Product information and accessible sources checked on 14 October 2026.
Buying decision: list the complete reusable sets for each service and establish their longest observed return windows first. Then assess Fomos Foster 8 L or Fomos Foster 12 L using supported load suitability for your specific instruments. Verify the current manual, specifications and availability before ordering.